Add "ANSI Common Lisp Standard" (#6670)

Co-authored-by: ImVector <59611597+LuigiImVector@users.noreply.github.com>

books/free-programming-books-langs.md

@@ -1454,6 +1454,7 @@ That section got so big, we decided to split it into its own file, the [BY SUBJE
 
 ### Lisp
 
+* [ANSI Common Lisp Standard (draft version 15.17R, X3J13/94-101R)](https://franz.com/support/documentation/cl-ansi-standard-draft-w-sidebar.pdf) (PDF)
 * [Basic Lisp Techniques](http://franz.com/resources/educational_resources/cooper.book.pdf) - David J. Cooper, Jr. (PDF)
 * [Casting Spels in Lisp](http://www.lisperati.com/casting.html)
 * [Common Lisp: A Gentle Introduction to Symbolic Computation](http://www.cs.cmu.edu/~dst/LispBook/) - David S. Touretzky (PDF, PS)