Update free-programming-books.md

Added C# book
Merge pull request #483 from MHM5000/master

LaTeX and Persian Conflict $482
Reorders the "Non dépendant du langage" section

- Add navigation links
- Sort by alphabetical order
Merge pull request #484 from ericguirbal/fr

Reorders the "Non dépendant du langage" section
C#
Merge remote-tracking branch 'upstream/master'