---
layout: docs
title: Plugins
prev_section: assets
next_section: extras
permalink: /docs/plugins/
---

Jekyll has a plugin system with hooks that allow you to create custom generated
content specific to your site. You can run custom code for your site without
having to modify the Jekyll source itself.

<div class="note info">
  <h5>Plugins on GitHub Pages</h5>
  <p>
    <a href="http://pages.github.com/">GitHub Pages</a> is powered by Jekyll,
    however all Pages sites are generated using the <code>--safe</code> option
    to disable custom plugins for security reasons. Unfortunately, this means
    your plugins won’t work if you’re deploying to GitHub Pages.<br><br>
    You can still use GitHub Pages to publish your site, but you’ll need to
    convert the site locally and push the generated static files to your GitHub
    repository instead of the Jekyll source files.
  </p>
</div>

## Installing a plugin

You have 2 options for installing plugins:

1. In your site source root, make a `_plugins` directory. Place your plugins here.
    Any file ending in `*.rb` inside this directory will be loaded before Jekyll
    generates your site.
2. In your `_config.yml` file, add a new array with the key `gems` and the values
    of the gem names of the plugins you'd like to use. An example:

        gems: [jekyll-test-plugin, jekyll-jsonify, jekyll-assets]
        # This will require each of these gems automatically.

<div class="note info">
  <h5>
    <code>_plugins</code> and <code>gems</code>
    can be used simultaneously
  </h5>
  <p>
    You may use both of the aforementioned plugin options simultaneously in the
    same site if you so choose. Use of one does not restrict the use of the other
  </p>
</div>

In general, plugins you make will fall into one of three categories:

1. Generators
2. Converters
3. Tags

## Generators

You can create a generator when you need Jekyll to create additional content
based on your own rules.

A generator is a subclass of `Jekyll::Generator` that defines a `generate`
method, which receives an instance of
[`Jekyll::Site`]({{ site.repository }}/blob/master/lib/jekyll/site.rb).

Generation is triggered for its side-effects, the return value of `generate` is
ignored. Jekyll does not assume any particular side-effect to happen, it just
runs the method.

Generators run after Jekyll has made an inventory of the existing content, and
before the site is generated. Pages with YAML front-matters are stored as
instances of
[`Jekyll::Page`]({{ site.repository }}/blob/master/lib/jekyll/page.rb)
and are available via `site.pages`. Static files become instances of
[`Jekyll::StaticFile`]({{ site.repository }}/blob/master/lib/jekyll/static_file.rb)
and are available via `site.static_files`. See
[`Jekyll::Site`]({{ site.repository }}/blob/master/lib/jekyll/site.rb)
for more details.

For instance, a generator can inject values computed at build time for template
variables. In the following example the template `reading.html` has two
variables `ongoing` and `done` that we fill in the generator:

{% highlight ruby %}
module Reading
  class Generator < Jekyll::Generator
    def generate(site)
      ongoing, done = Book.all.partition(&:ongoing?)

      reading = site.pages.detect {|page| page.name == 'reading.html'}
      reading.data['ongoing'] = ongoing
      reading.data['done'] = done
    end
  end
end
{% endhighlight %}

This is a more complex generator that generates new pages:

{% highlight ruby %}
module Jekyll

  class CategoryPage < Page
    def initialize(site, base, dir, category)
      @site = site
      @base = base
      @dir = dir
      @name = 'index.html'

      self.process(@name)
      self.read_yaml(File.join(base, '_layouts'), 'category_index.html')
      self.data['category'] = category

      category_title_prefix = site.config['category_title_prefix'] || 'Category: '
      self.data['title'] = "#{category_title_prefix}#{category}"
    end
  end

  class CategoryPageGenerator < Generator
    safe true

    def generate(site)
      if site.layouts.key? 'category_index'
        dir = site.config['category_dir'] || 'categories'
        site.categories.keys.each do |category|
          site.pages << CategoryPage.new(site, site.source, File.join(dir, category), category)
        end
      end
    end
  end

end
{% endhighlight %}

In this example, our generator will create a series of files under the
`categories` directory for each category, listing the posts in each category
using the `category_index.html` layout.

Generators are only required to implement one method:

<div class="mobile-side-scroller">
<table>
  <thead>
    <tr>
      <th>Method</th>
      <th>Description</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <td>
        <p><code>generate</code></p>
      </td>
      <td>
        <p>Generates content as a side-effect.</p>
      </td>
    </tr>
  </tbody>
</table>
</div>

## Converters

If you have a new markup language you’d like to use with your site, you can
include it by implementing your own converter. Both the Markdown and Textile
markup languages are implemented using this method.

<div class="note info">
  <h5>Remember your YAML front-matter</h5>
  <p>
    Jekyll will only convert files that have a YAML header at the top, even for
    converters you add using a plugin.
  </p>
</div>

Below is a converter that will take all posts ending in `.upcase` and process
them using the `UpcaseConverter`:

{% highlight ruby %}
module Jekyll
  class UpcaseConverter < Converter
    safe true
    priority :low

    def matches(ext)
      ext =~ /^\.upcase$/i
    end

    def output_ext(ext)
      ".html"
    end

    def convert(content)
      content.upcase
    end
  end
end
{% endhighlight %}

Converters should implement at a minimum 3 methods:

<div class="mobile-side-scroller">
<table>
  <thead>
    <tr>
      <th>Method</th>
      <th>Description</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <td>
        <p><code>matches</code></p>
      </td>
      <td><p>
        Does the given extension match this converter’s list of acceptable
        extensions? Takes one argument: the file’s extension (including the
        dot). Must return <code>true</code> if it matches, <code>false</code>
        otherwise.
      </p></td>
    </tr>
    <tr>
      <td>
        <p><code>output_ext</code></p>
      </td>
      <td><p>
        The extension to be given to the output file (including the dot).
        Usually this will be <code>".html"</code>.
      </p></td>
    </tr>
    <tr>
      <td>
        <p><code>convert</code></p>
      </td>
      <td><p>
        Logic to do the content conversion. Takes one argument: the raw content
        of the file (without YAML front matter). Must return a String.
      </p></td>
    </tr>
  </tbody>
</table>
</div>

In our example, `UpcaseConverter#matches` checks if our filename extension is
`.upcase`, and will render using the converter if it is. It will call
`UpcaseConverter#convert` to process the content. In our simple converter we’re
simply uppercasing the entire content string. Finally, when it saves the page,
it will do so with a `.html` extension.

## Tags

If you’d like to include custom liquid tags in your site, you can do so by
hooking into the tagging system. Built-in examples added by Jekyll include the
`highlight` and `include` tags. Below is an example of a custom liquid tag that
will output the time the page was rendered:

{% highlight ruby %}
module Jekyll
  class RenderTimeTag < Liquid::Tag

    def initialize(tag_name, text, tokens)
      super
      @text = text
    end

    def render(context)
      "#{@text} #{Time.now}"
    end
  end
end

Liquid::Template.register_tag('render_time', Jekyll::RenderTimeTag)
{% endhighlight %}

At a minimum, liquid tags must implement:

<div class="mobile-side-scroller">
<table>
  <thead>
    <tr>
      <th>Method</th>
      <th>Description</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <td>
        <p><code>render</code></p>
      </td>
      <td>
        <p>Outputs the content of the tag.</p>
      </td>
    </tr>
  </tbody>
</table>
</div>

You must also register the custom tag with the Liquid template engine as
follows:

{% highlight ruby %}
Liquid::Template.register_tag('render_time', Jekyll::RenderTimeTag)
{% endhighlight %}

In the example above, we can place the following tag anywhere in one of our
pages:

{% highlight ruby %}
{% raw %}
<p>{% render_time page rendered at: %}</p>
{% endraw %}
{% endhighlight %}

And we would get something like this on the page:

{% highlight html %}
<p>page rendered at: Tue June 22 23:38:47 –0500 2010</p>
{% endhighlight %}

### Liquid filters

You can add your own filters to the Liquid template system much like you can add
tags above. Filters are simply modules that export their methods to liquid. All
methods will have to take at least one parameter which represents the input of
the filter. The return value will be the output of the filter.

{% highlight ruby %}
module Jekyll
  module AssetFilter
    def asset_url(input)
      "http://www.example.com/#{input}?#{Time.now.to_i}"
    end
  end
end

Liquid::Template.register_filter(Jekyll::AssetFilter)
{% endhighlight %}

<div class="note">
  <h5>ProTip™: Access the site object using Liquid</h5>
  <p>
    Jekyll lets you access the <code>site</code> object through the
    <code>context.registers</code> feature of Liquid. For example, you can
    access the global configuration file <code>_config.yml</code> using
    <code>context.registers.config</code>.
  </p>
</div>

### Flags

There are two flags to be aware of when writing a plugin:

<div class="mobile-side-scroller">
<table>
  <thead>
    <tr>
      <th>Flag</th>
      <th>Description</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <td>
        <p><code>safe</code></p>
      </td>
      <td>
        <p>
          A boolean flag that informs Jekyll whether this plugin may be safely
          executed in an environment where arbitrary code execution is not
          allowed. This is used by GitHub Pages to determine which core plugins
          may be used, and which are unsafe to run. If your plugin does not
          allow for arbitrary code, execution, set this to <code>true</code>.
          GitHub Pages still won’t load your plugin, but if you submit it for
          inclusion in core, it’s best for this to be correct!
        </p>
      </td>
    </tr>
    <tr>
      <td>
        <p><code>priority</code></p>
      </td>
      <td>
        <p>
          This flag determines what order the plugin is loaded in. Valid values
          are: <code>:lowest</code>, <code>:low</code>, <code>:normal</code>,
          <code>:high</code>, and <code>:highest</code>. Highest priority
          matches are applied first, lowest priority are applied last.
        </p>
      </td>
    </tr>
  </tbody>
</table>
</div>

To use one of the example plugins above as an illustration, here is how you’d
specify these two flags:

{% highlight ruby %}
module Jekyll
  class UpcaseConverter < Converter
    safe true
    priority :low
    ...
  end
end
{% endhighlight %}

## Available Plugins

You can find a few useful plugins at the following locations:

#### Generators

- [ArchiveGenerator by Ilkka Laukkanen](https://gist.github.com/707909): Uses [this archive page](https://gist.github.com/707020) to generate archives.
- [LESS.js Generator by Andy Fowler](https://gist.github.com/642739): Renders LESS.js files during generation.
- [Version Reporter by Blake Smith](https://gist.github.com/449491): Creates a version.html file containing the Jekyll version.
- [Sitemap.xml Generator by Michael Levin](https://github.com/kinnetica/jekyll-plugins): Generates a sitemap.xml file by traversing all of the available posts and pages.
- [Full-text search by Pascal Widdershoven](https://github.com/PascalW/jekyll_indextank): Adds full-text search to your Jekyll site with a plugin and a bit of JavaScript.
- [AliasGenerator by Thomas Mango](https://github.com/tsmango/jekyll_alias_generator): Generates redirect pages for posts when an alias is specified in the YAML Front Matter.
- [Pageless Redirect Generator by Nick Quinlan](https://github.com/nquinlan/jekyll-pageless-redirects): Generates redirects based on files in the Jekyll root, with support for htaccess style redirects.
- [Projectlist by Frederic Hemberger](https://github.com/fhemberger/jekyll-projectlist): Renders files in a directory as a single page instead of separate posts.
- [RssGenerator by Assaf Gelber](https://github.com/agelber/jekyll-rss): Automatically creates an RSS 2.0 feed from your posts.

#### Converters

- [Jade plugin by John Papandriopoulos](https://github.com/snappylabs/jade-jekyll-plugin): Jade converter for Jekyll.
- [HAML plugin by Sam Z](https://gist.github.com/517556): HAML converter for Jekyll.
- [HAML-Sass Converter by Adam Pearson](https://gist.github.com/481456): Simple HAML-Sass converter for Jekyll. [Fork](https://gist.github.com/528642) by Sam X.
- [Sass SCSS Converter by Mark Wolfe](https://gist.github.com/960150): Sass converter which uses the new CSS compatible syntax, based Sam X’s fork above.
- [LESS Converter by Jason Graham](https://gist.github.com/639920): Convert LESS files to CSS.
- [LESS Converter by Josh Brown](https://gist.github.com/760265): Simple LESS converter.
- [Upcase Converter by Blake Smith](https://gist.github.com/449463): An example Jekyll converter.
- [CoffeeScript Converter by phaer](https://gist.github.com/959938): A [CoffeeScript](http://coffeescript.org) to Javascript converter.
- [Markdown References by Olov Lassus](https://github.com/olov/jekyll-references): Keep all your markdown reference-style link definitions in one \_references.md file.
- [Stylus Converter](https://gist.github.com/988201): Convert .styl to .css.
- [ReStructuredText Converter](https://github.com/xdissent/jekyll-rst): Converts ReST documents to HTML with Pygments syntax highlighting.
- [Jekyll-pandoc-plugin](https://github.com/dsanson/jekyll-pandoc-plugin): Use pandoc for rendering markdown.
- [Jekyll-pandoc-multiple-formats](https://github.com/fauno/jekyll-pandoc-multiple-formats) by [edsl](https://github.com/edsl): Use pandoc to generate your site in multiple formats. Supports pandoc’s markdown extensions.
- [ReStructuredText Converter](https://github.com/xdissent/jekyll-rst): Converts ReST documents to HTML with Pygments syntax highlighting.
- [Transform Layouts](https://gist.github.com/1472645): Allows HAML layouts (you need a HAML Converter plugin for this to work).

#### Filters

- [Truncate HTML](https://github.com/MattHall/truncatehtml) by [Matt Hall](http://codebeef.com): A Jekyll filter that truncates HTML while preserving markup structure.
- [Domain Name Filter by Lawrence Woodman](https://github.com/LawrenceWoodman/domain_name-liquid_filter): Filters the input text so that just the domain name is left.
- [Summarize Filter by Mathieu Arnold](https://gist.github.com/731597): Remove markup after a `<div id="extended">` tag.
- [URL encoding by James An](https://gist.github.com/919275): Percent encoding for URIs.
- [JSON Filter](https://gist.github.com/1850654) by [joelverhagen](https://github.com/joelverhagen): Filter that takes input text and outputs it as JSON. Great for rendering JavaScript.
- [i18n_filter](https://github.com/gacha/gacha.id.lv/blob/master/_plugins/i18n_filter.rb): Liquid filter to use I18n localization.
- [Smilify](https://github.com/SaswatPadhi/jekyll_smilify) by [SaswatPadhi](https://github.com/SaswatPadhi): Convert text emoticons in your content to themeable smiley pics ([Demo](http://saswatpadhi.github.com/)).
- [Read in X Minutes](https://gist.github.com/zachleat/5792681) by [zachleat](https://github.com/zachleat): Estimates the reading time of a string (for blog post content).
- [Jekyll-timeago](https://github.com/markets/jekyll-timeago): Converts a time value to the time ago in words.
- [pluralize](https://github.com/bdesham/pluralize): Easily combine a number and a word into a gramatically-correct amount like “1 minute” or “2 minute**s**”.
- [reading_time](https://github.com/bdesham/reading_time): Count words and estimate reading time for a piece of text, ignoring HTML elements that are unlikely to contain running text.
- [Table of Content Generator](https://github.com/dafi/jekyll-toc-generator): Generate the HTML code containing a table of content (TOC), the TOC can be customized in many way, for example you can decide which pages can be without TOC.

#### Tags

- [Delicious Plugin by Christian Hellsten](https://github.com/christianhellsten/jekyll-plugins): Fetches and renders bookmarks from delicious.com.
- [Ultraviolet Plugin by Steve Alex](https://gist.github.com/480380): Jekyll tag for the [Ultraviolet](http://ultraviolet.rubyforge.org/) code highligher.
- [Tag Cloud Plugin by Ilkka Laukkanen](https://gist.github.com/710577): Generate a tag cloud that links to tag pages.
- [GIT Tag by Alexandre Girard](https://gist.github.com/730347): Add Git activity inside a list.
- [MathJax Liquid Tags by Jessy Cowan-Sharp](https://gist.github.com/834610): Simple liquid tags for Jekyll that convert inline math and block equations to the appropriate MathJax script tags.
- [Non-JS Gist Tag by Brandon Tilley](https://gist.github.com/1027674) A Liquid tag that embeds Gists and shows code for non-JavaScript enabled browsers and readers.
- [Render Time Tag by Blake Smith](https://gist.github.com/449509): Displays the time a Jekyll page was generated.
- [Status.net/OStatus Tag by phaer](https://gist.github.com/912466): Displays the notices in a given status.net/ostatus feed.
- [Raw Tag by phaer](https://gist.github.com/1020852): Keeps liquid from parsing text betweeen `raw` tags.
- [Embed.ly client by Robert Böhnke](https://github.com/robb/jekyll-embedly-client): Autogenerate embeds from URLs using oEmbed.
- [Logarithmic Tag Cloud](https://gist.github.com/2290195): Flexible. Logarithmic distribution. Documentation inline.
- [oEmbed Tag by Tammo van Lessen](https://gist.github.com/1455726): Enables easy content embedding (e.g. from YouTube, Flickr, Slideshare) via oEmbed.
- [FlickrSetTag by Thomas Mango](https://github.com/tsmango/jekyll_flickr_set_tag): Generates image galleries from Flickr sets.
- [Tweet Tag by Scott W. Bradley](https://github.com/scottwb/jekyll-tweet-tag): Liquid tag for [Embedded Tweets](https://dev.twitter.com/docs/embedded-tweets) using Twitter’s shortcodes.
- [Jekyll-contentblocks](https://github.com/rustygeldmacher/jekyll-contentblocks): Lets you use Rails-like content_for tags in your templates, for passing content from your posts up to your layouts.
- [Generate YouTube Embed](https://gist.github.com/1805814) by [joelverhagen](https://github.com/joelverhagen): Jekyll plugin which allows you to embed a YouTube video in your page with the YouTube ID. Optionally specify width and height dimensions. Like “oEmbed Tag” but just for YouTube.
- [Jekyll-beastiepress](https://github.com/okeeblow/jekyll-beastiepress): FreeBSD utility tags for Jekyll sites.
- [Jsonball](https://gist.github.com/1895282): Reads json files and produces maps for use in Jekyll files.
- [Bibjekyll](https://github.com/pablooliveira/bibjekyll): Render BibTeX-formatted bibliographies/citations included in posts and pages using bibtex2html.
- [Jekyll-citation](https://github.com/archome/jekyll-citation): Render BibTeX-formatted bibliographies/citations included in posts and pages (pure Ruby).
- [Jekyll Dribbble Set Tag](https://github.com/ericdfields/Jekyll-Dribbble-Set-Tag): Builds Dribbble image galleries from any user.
- [Debbugs](https://gist.github.com/2218470): Allows posting links to Debian BTS easily.
- [Refheap_tag](https://github.com/aburdette/refheap_tag): Liquid tag that allows embedding pastes from [refheap](https://refheap.com).
- [Jekyll-devonly_tag](https://gist.github.com/2403522): A block tag for including markup only during development.
- [JekyllGalleryTag](https://github.com/redwallhp/JekyllGalleryTag) by [redwallhp](https://github.com/redwallhp): Generates thumbnails from a directory of images and displays them in a grid.
- [Youku and Tudou Embed](https://gist.github.com/Yexiaoxing/5891929): Liquid plugin for embedding Youku and Tudou videos.
- [Jekyll-swfobject](https://github.com/sectore/jekyll-swfobject): Liquid plugin for embedding Adobe Flash files (.swf) using [SWFObject](http://code.google.com/p/swfobject/).
- [Jekyll Picture Tag](https://github.com/robwierzbowski/jekyll-picture-tag): Easy responsive images for Jekyll. Based on the proposed [`<picture>`](http://picture.responsiveimages.org/) element, polyfilled with Scott Jehl’s [Picturefill](https://github.com/scottjehl/picturefill).
- [Jekyll Image Tag](https://github.com/robwierzbowski/jekyll-image-tag): Better images for Jekyll. Save image presets, generate resized images, and add classes, alt text, and other attributes.
- [Ditaa Tag](https://github.com/matze/jekyll-ditaa) by [matze](https://github.com/matze): Renders ASCII diagram art into PNG images and inserts a figure tag.
- [Good Include](https://github.com/penibelst/jekyll-good-include) by [Anatol Broder](http://penibelst.de/): Strips newlines and whitespaces from the end of include files before processing.
- [Jekyll Suggested Tweet](https://github.com/davidensinger/jekyll-suggested-tweet) by [David Ensinger](https://github.com/davidensinger/): A Liquid tag for Jekyll that allows for the embedding of suggested tweets via Twitter’s Web Intents API.
- [Jekyll Date Chart](https://github.com/GSI/jekyll_date_chart) by [GSI](https://github.com/GSI): Block that renders date line charts based on textile-formatted tables.
- [Jekyll Image Encode](https://github.com/GSI/jekyll_image_encode) by [GSI](https://github.com/GSI): Tag that renders base64 codes of images fetched from the web.
- [Jekyll Quick Man](https://github.com/GSI/jekyll_quick_man) by [GSI](https://github.com/GSI): Tag that renders pretty links to man page sources on the internet.

#### Collections

- [Jekyll Plugins by Recursive Design](http://recursive-design.com/projects/jekyll-plugins/): Plugins to generate Project pages from GitHub readmes, a Category page, and a Sitemap generator.
- [Company website and blog plugins](https://github.com/flatterline/jekyll-plugins) by Flatterline, a [Ruby on Rails development company](http://flatterline.com/): Portfolio/project page generator, team/individual page generator, an author bio liquid tag for use on posts, and a few other smaller plugins.
- [Jekyll plugins by Aucor](https://github.com/aucor/jekyll-plugins): Plugins for trimming unwanted newlines/whitespace and sorting pages by weight attribute.

#### Other

- [Pygments Cache Path by Raimonds Simanovskis](https://github.com/rsim/blog.rayapps.com/blob/master/_plugins/pygments_cache_patch.rb): Plugin to cache syntax-highlighted code from Pygments.
- [Draft/Publish Plugin by Michael Ivey](https://gist.github.com/49630): Save posts as drafts.
- [Growl Notification Generator by Tate Johnson](https://gist.github.com/490101): Send Jekyll notifications to Growl.
- [Growl Notification Hook by Tate Johnson](https://gist.github.com/525267): Better alternative to the above, but requires his “hook” fork.
- [Related Posts by Lawrence Woodman](https://github.com/LawrenceWoodman/related_posts-jekyll_plugin): Overrides `site.related_posts` to use categories to assess relationship.
- [Tiered Archives by Eli Naeher](https://gist.github.com/88cda643aa7e3b0ca1e5): Create tiered template variable that allows you to group archives by year and month.
- [Jekyll-localization](https://github.com/blackwinter/jekyll-localization): Jekyll plugin that adds localization features to the rendering engine.
- [Jekyll-rendering](https://github.com/blackwinter/jekyll-rendering): Jekyll plugin to provide alternative rendering engines.
- [Jekyll-pagination](https://github.com/blackwinter/jekyll-pagination): Jekyll plugin to extend the pagination generator.
- [Jekyll-tagging](https://github.com/pattex/jekyll-tagging): Jekyll plugin to automatically generate a tag cloud and tag pages.
- [Jekyll-scholar](https://github.com/inukshuk/jekyll-scholar): Jekyll extensions for the blogging scholar.
- [Jekyll-asset_bundler](https://github.com/moshen/jekyll-asset_bundler): Bundles and minifies JavaScript and CSS.
- [Jekyll-assets](http://ixti.net/jekyll-assets/) by [ixti](https://github.com/ixti): Rails-alike assets pipeline (write assets in CoffeeScript, Sass, LESS etc; specify dependencies for automatic bundling using simple declarative comments in assets; minify and compress; use JST templates; cache bust; and many-many more).
- [File compressor](https://gist.github.com/2758691) by [mytharcher](https://github.com/mytharcher): Compress HTML and JavaScript files on site build.
- [Jekyll-minibundle](https://github.com/tkareine/jekyll-minibundle): Asset bundling and cache busting using external minification tool of your choice. No gem dependencies.
- [Singlepage-jekyll](https://github.com/JCB-K/singlepage-jekyll) by [JCB-K](https://github.com/JCB-K): Turns Jekyll into a dynamic one-page website.
- [generator-jekyllrb](https://github.com/robwierzbowski/generator-jekyllrb): A generator that wraps Jekyll in [Yeoman](http://yeoman.io/), a tool collection and workflow for builing modern web apps.
- [grunt-jekyll](https://github.com/dannygarcia/grunt-jekyll): A straightforward [Grunt](http://gruntjs.com/) plugin for Jekyll.
- [jekyll-postfiles](https://github.com/indirect/jekyll-postfiles): Add `_postfiles` directory and {% raw %}`{{ postfile }}`{% endraw %} tag so the files a post refers to will always be right there inside your repo.

<div class="note info">
  <h5>Jekyll Plugins Wanted</h5>
  <p>
    If you have a Jekyll plugin that you would like to see added to this list,
    you should <a href="../contributing/">read the contributing page</a> to find
    out how to make that happen.
  </p>
</div>