Update free-programming-books-langs.md (#9385)

* Update free-programming-books-langs.md

Add a Clojure book

* Remove trailing slash in URL

books/free-programming-books-langs.md

@@ -568,6 +568,7 @@ Books on general-purpose programming that don't focus on a specific language are
 ### Clojure
 
 * [A Brief Beginner’s Guide To Clojure](http://www.unexpected-vortices.com/clojure/brief-beginners-guide/)
+* [Clojure](https://clojure-book.gitlab.io) - Karthikeyan A K
 * [Clojure - Functional Programming for the JVM](http://java.ociweb.com/mark/clojure/article.html) - R. Mark Volkmann
 * [Clojure by Example](https://kimh.github.io/clojure-by-example/) - Hirokuni Kim
 * [Clojure community-driven documentation](http://clojure-doc.org)