Added some books and section (#8067)

* added a few new books along with a new programming language section

* added a few new books along with a new programming language section

* added books for LUA,Markdown,YAML and created a new section for YAML

* added books for LUA,Markdown,YAML and created a new section for YAML

* added books for LUA,Markdown,YAML and created a new section for YAML

* added books for LUA,Markdown,YAML and created a new section for YAML

* added books for LUA,Markdown,YAML and created a new section for YAML

* updated books collection

Removed the Lua book as requested

books/free-programming-books-langs.md

@@ -1498,6 +1498,7 @@ That section got so big, we decided to split it into its own file, the [BY SUBJE
 
 ### Markdown
 
+* [bookdown: Authoring Books and Technical Documents with R Markdown](https://bookdown.org) - Yihui Xie (HTML) [(PDF, EPUB, MOBI)] (https://bookdown.org/yihui/bookdown/)
 * [Learn Markdown](https://www.gitbook.com/book/gitbookio/markdown/details) - Sammy P., Aaron O. (PDF) (EPUB) (MOBI)
 
 
@@ -2546,3 +2547,8 @@ That section got so big, we decided to split it into its own file, the [BY SUBJE
 * [Application Development with Harbour](https://en.wikibooks.org/wiki/Application_Development_with_Harbour) - Wikibooks
 * [CA-Clipper 5.2 Norton Guide](https://web.archive.org/web/20190516192814/http://www.ousob.com/ng/clguide/)
 * [Clipper Tutorial: a Guide to Open Source Clipper(s)](https://en.wikibooks.org/wiki/Clipper_Tutorial%3A_a_Guide_to_Open_Source_Clipper(s)) - Wikibooks
+
+
+### YAML
+
+* [YAML Tutorial](https://www.tutorialspoint.com/yaml/yaml_tutorial.pdf) - TutorialsPoint (PDF)