Add `Git Cookbook` by Dennis Kaarsemaker (#6732)

* Add `Git Cookbook` by Dennis Kaarsemaker

* linking to `about.html` said the boss to fit as book

books/free-programming-books-langs.md

@@ -791,6 +791,7 @@ That section got so big, we decided to split it into its own file, the [BY SUBJE
 * [A Visual Git Reference](http://marklodato.github.io/visual-git-guide/index-en.html) - Mark Lodato
 * [Conversational Git](http://blog.anvard.org/conversational-git/)
 * [git - the simple guide](http://rogerdudler.github.io/git-guide/)
+* [Git cookbook](https://git.seveas.net/about.html) - Dennis Kaarsemaker (HTML)
 * [Git for Computer Scientists](http://eagain.net/articles/git-for-computer-scientists/)
 * [Git From The Bottom Up](https://jwiegley.github.io/git-from-the-bottom-up/) - J. Wiegley
 * [Git Immersion](http://gitimmersion.com)