Add Learn Ruby on Rails: Book Two (#8590)

books/free-programming-books-langs.md

@@ -2173,6 +2173,7 @@ That section got so big, we decided to split it into its own file, the [BY SUBJE
 * [Essential Ruby on Rails](https://www.programming-books.io/essential/rubyonrails/) - Krzysztof Kowalczyk, StackOverflow Contributors
 * [Kestrels, Quirky Birds, and Hopeless Egocentricity](https://leanpub.com/combinators/read) - Reg Braithwaite
 * [Learn Ruby on Rails: Book One](https://learn-rails.com/content/learnrails1) - Daniel Kehoe
+* [Learn Ruby on Rails: Book Two](https://learn-rails.com/content/learnrails2) - Daniel Kehoe
 * [Objects on Rails](https://web.archive.org/web/20190319201525/http://objectsonrails.com/) - Avdi Grimm
 * [Rails Girls Guides](http://guides.railsgirls.com)
 * [Rails Style Guide](https://rails.rubystyle.guide) - Bozhidar Batsov