Add "Programming Fundementals" book (#5682)

* feat: add "Programming Fundamentals" book

* feat: modify Programming Fundamentals URL

Co-authored-by: Alexandre Vu <UVUALEX@VP1333718.ile.mtl.qc.ca>

books/free-programming-books-subjects.md

@@ -499,6 +499,7 @@ Books that cover a specific programming language can be found in the  [BY PROGRA
 * [PNG: The Definitive Guide](http://www.libpng.org/pub/png/book/)
 * [Pointers And Memory](http://cslibrary.stanford.edu/102/PointersAndMemory.pdf) (PDF)
 * [Principles of Computer System Design](http://ocw.mit.edu/resources/res-6-004-principles-of-computer-system-design-an-introduction-spring-2009/online-textbook/part_ii_open_5_0.pdf) (PDF)
+* [Programming Fundamentals](https://press.rebus.community/programmingfundamentals/) - Kenneth Leroy Busbee, Dave Braunschweig
 * [Programming with Unicode](http://unicodebook.readthedocs.org)
 * [Real-World Maintainable Software](https://www.oreilly.com/ideas/real-world-maintainable-software) - Abraham Marin-Perez
 * [Record-Playback Test Automation: Sahi & Selenium IDE: Critical Evaluation of Record-Playback Automation Tools](https://leanpub.com/manualToAutomatedWithSeleniumIDEAndSahi) - Shashikant Jagtap  *(Leanpub account or valid email requested)*