Mention Codespace in contribution guide

Author: edwinv

guides/source/contributing_to_ruby_on_rails.md

@@ -187,6 +187,10 @@ Contributing to the Rails Code
 
 To move on from submitting bugs to helping resolve existing issues or contributing your own code to Ruby on Rails, you _must_ be able to run its test suite. In this section of the guide, you'll learn how to set up the tests on your computer.
 
+#### The Easiest Way
+
+Start a Github Codespace from the repository and start developing right away from the browser IDE or in your local VScode. The Codespace is initialized with all required dependencies and allows you to run all tests.
+
 #### The Easy Way
 
 The easiest and recommended way to get a development environment ready to hack is to use the [rails-dev-box](https://github.com/rails/rails-dev-box).