Added "Learn Programming" to Language Agnostic -> Misc (#2938)

free-programming-books.md

@@ -513,6 +513,7 @@
 * [Image Processing in C: Analyzing and Enhancing Digital Images](http://homepages.inf.ed.ac.uk/rbf/BOOKS/PHILLIPS/) - Dwayne Phillips
 * [Information Technology and the Networked Economy](http://florida.theorangegrove.org/og/file/49843a6a-9a9d-4bad-b4d4-d053f9cdf73e/1/InfoTechNetworkedEconomy.pdf) (PDF)
 * [IRPF90 Fortran code generator](https://www.gitbook.com/book/scemama/irpf90/details) - Anthony Scemama
+* [Learn Programming](https://progbook.org) - Antti Salonen
 * [Learn to Program](https://pine.fm/LearnToProgram/)
 * [Learning 30 Technologies in 30 Days: A Developer Challenge](https://blog.openshift.com/learning-30-technologies-in-30-days-a-developer-challenge/) - Shekhar Gulati
 * [Learning Docker](https://www.packtpub.com/packt/free-ebook/learning-docker) - Pethuru Raj, Jeeva S. Chelladhurai & Vinod Singh, Packt. (email address *requested*, not required)