README.adoc in relaton-iso-bib-1.16.1 vs README.adoc in relaton-iso-bib-1.16.2

@@ -1,11 +1,9 @@
 = RelatonIsoBib
 
 image:https://img.shields.io/gem/v/relaton-iso-bib.svg["Gem Version", link="https://rubygems.org/gems/relaton-iso-bib"]
-image:https://github.com/relaton/relaton-iso-bib/workflows/macos/badge.svg["Build Status (macOS)", link="https://github.com/relaton/relaton-iso-bib/actions?workflow=macos"]
-image:https://github.com/relaton/relaton-iso-bib/workflows/windows/badge.svg["Build Status (Windows)", link="https://github.com/relaton/relaton-iso-bib/actions?workflow=windows"]
-image:https://github.com/relaton/relaton-iso-bib/workflows/ubuntu/badge.svg["Build Status (Ubuntu)", link="https://github.com/relaton/relaton-iso-bib/actions?workflow=ubuntu"]
+image:https://github.com/relaton/relaton-iso-bib/workflows/rake/badge.svg["Build Status (macOS)", link="https://github.com/relaton/relaton-iso-bib/actions?workflow=rake"]
 image:https://codeclimate.com/github/relaton/relaton-iso-bib/badges/gpa.svg["Code Climate", link="https://codeclimate.com/github/relaton/relaton-iso-bib"]
 image:https://img.shields.io/github/issues-pr-raw/relaton/relaton-iso-bib.svg["Pull Requests", link="https://github.com/relaton/relaton-iso-bib/pulls"]
 image:https://img.shields.io/github/commits-since/relaton/relaton-iso-bib/latest.svg["Commits since latest",link="https://github.com/relaton/relaton-iso-bib/releases"]
 
 IsoBib is a Ruby gem that implements the https://github.com/metanorma/metanorma-model-iso#iso-bibliographic-item[IsoBibliographicItem model].
@@ -27,16 +25,27 @@
 
     $ gem install relaton-iso-bib
 
 == Usage
 
-=== Create ISO bibliographic item
+=== Configuration
 
+Configuration is optional. The available option is `logger` which is a `Logger` instance. By default, the logger is `Logger.new($stderr)` with `Logger::WARN` level. To change the logger level, use `RelatonIsoBib.configure` block.
+
 [source,ruby]
 ----
 require 'relaton_iso_bib'
 => true
 
+RelatonIsoBib.configure do |config|
+  config.logger.level = Logger::DEBUG
+end
+----
+
+=== Create ISO bibliographic item
+
+[source,ruby]
+----
 hash = YAML.load_file "spec/examples/iso_bib_item.yml"
 => {
     "schema-version"=>"v1.0.0",
     "id"=>"ISO/TC211",
     "title"=>[