Add OCaml From the Ground Up (#5829)

* Add OCaml From the Ground Up

* Remove trailing slash

books/free-programming-books-langs.md

@@ -1541,6 +1541,7 @@ That section got so big, we decided to split it into its own file, the [BY SUBJE
 
 * [Developing Applications With Objective Caml](http://caml.inria.fr/pub/docs/oreilly-book/)
 * [Functional Programming in OCaml](https://www.cs.cornell.edu/courses/cs3110/2019sp/textbook/) - Michael R. Clarkson
+* [OCaml From the Ground Up](https://ocamlbook.org) - Daniil Baturin (HTML) (:construction: *in process*)
 * [OCaml Scientific Computing](https://ocaml.xyz/book/) - Liang Wang, Jianxin Zhao (HTML) (:construction: *in process*)
 * [Real World OCaml](https://dev.realworldocaml.org/toc.html)
 * [Think OCaml](http://greenteapress.com/thinkocaml/index.html) - Allen B. Downey and Nicholas Monje