Adding C++ / Learning C++ eBook (#6275)

* Add C++ / Learning C++ eBook

* Update books/free-programming-books-langs.md

Co-authored-by: David Ordás <3125580+davorpa@users.noreply.github.com>

Co-authored-by: Eric Hellman <eric@hellman.net>
Co-authored-by: David Ordás <3125580+davorpa@users.noreply.github.com>

books/free-programming-books-langs.md

@@ -502,6 +502,7 @@ That section got so big, we decided to split it into its own file, the [BY SUBJE
 * [Introduction to Design Patterns in C++ with Qt 4](http://ptgmedia.pearsoncmg.com/images/9780131879058/downloads/0131879057_Ezust_book.pdf) - Alan Ezust, Paul Ezust (PDF)
 * [Joint Strike Fighter, C++ Coding Standards, by Bjarne Stroustrup](http://www.stroustrup.com/JSF-AV-rules.pdf) (PDF)
 * [LearnCpp.com](https://www.learncpp.com) (HTML)
+* [Learning C++ eBook](https://riptutorial.com/Download/cplusplus.pdf) - Compiled from StackOverflow Documentation (PDF)
 * [Matters Computational: Ideas, Algorithms, Source Code, by Jorg Arndt](http://www.jjj.de/fxt/fxtbook.pdf) (PDF)
 * [Open Data Structures (In C++)](http://opendatastructures.org/ods-cpp.pdf) - Pat Morin (PDF)
 * [Programming Fundamentals - A Modular Structured Approach using C++](https://learning.hccs.edu/faculty/ken.busbee/programming-fundamentals-a-modular-structured-approach-using-c) - Kenneth Leroy Busbee (PDF)