Added ANSI C books (#3872)

* Added ANSI C books

* Update free-programming-books-bg.md

* Update free-programming-books-bg.md

free-programming-books-bg.md

@@ -11,6 +11,8 @@
 
 ### C
 
+* [ANSI C - Курс за начинаещи](http://www.progstarter.com/index.php?option=com_content&view=article&id=8&Itemid=121&lang=bg) - Димо Петков
+* [ANSI C - Пълен справочник](http://progstarter.com/index.php?option=com_content&view=article&id=9&Itemid=122&lang=bg) - Димо Петков
 * [Програмиране = ++Алгоритми;](https://programirane.org/download-now/) - Преслав Наков и Панайот Добриков