README.md in importmap-rails-0.2.2 vs README.md in importmap-rails-0.2.3

@@ -54,10 +54,37 @@
 
 ```js
 import "trix"
 import md5 from "md5"
 console.log(md5("Hash it out"))
-``` 
+```
+
+
+## Preloading pinned modules
+
+To mitigate the waterfall effect where the browser has to load one file after another before it can get to the deepest nested import, we use [modulepreload links](https://developers.google.com/web/updates/2017/12/modulepreload) in [browsers that support it](https://caniuse.com/?search=modulepreload). Pinned modules are preloaded by default, but you can turn this off with `preload: false`.
+
+Example:
+
+```ruby
+# config/initializers/importmap.rb
+Rails.application.config.importmap.draw do
+  pin "trix", to: "https://cdn.skypack.dev/trix"
+  pin "md5", to: "https://cdn.skypack.dev/md5", preload: false
+end
+
+# app/views/layouts/application.html.erb
+<%= javascript_importmap_tags %> 
+
+# will include the following link before the importmap is setup:
+<link rel="modulepreload" href="https://cdn.skypack.dev/trix">
+...
+```
+
+
+## Caching the import map and preload modules
+
+The import map should be cached in production, and is so by default via the `config.importmap.cached` option that will be set to the same value as `config.action_controller.perform_caching`, unless explicitly set differently.
 
 
 ## Expected errors from using the es-module-shim
 
 While import maps are native in Chrome and Edge, they need a shim in other browsers that'll produce a JavaScript console error like `TypeError: Module specifier, 'application' does not start with "/", "./", or "../".`. This error is normal and does not have any user-facing consequences.