Add Single page apps in depth by Mixu (#4874)

* Add Single page apps in depth by Mixu

* try to fix formatting

* fix formatting

* trailing slash

Co-authored-by: Eric Hellman <eric@hellman.net>

free-programming-books.md

@@ -1734,10 +1734,11 @@ Kerridge (PDF) (email address *requested*, not required)
 * [Practical Modern JavaScript](https://github.com/mjavascript/practical-modern-javascript) - Nicolas Bevacqua (HTML)
 * [Professor Frisby’s Mostly Adequate Guide to Functional Programming](https://mostly-adequate.gitbooks.io/mostly-adequate-guide/content/) - Brian Lonsdorf (HTML)
 * [Robust Client-Side JavaScript](https://molily.de/robust-javascript/) - Matthias Schäfer (HTML, EPUB)
-* [Speaking JavaScript](http://speakingjs.com/es5/) - Dr. Axel Rauschmayer (HTML)
+* [Single page apps in depth](http://singlepageappbook.com) - Mixu (HTML)
+* [Speaking JavaScript](http://speakingjs.com/es5/) - Dr. Axel Rauschmayer
 * [Standard ECMA-262 ECMAScript 2016 Language Specification](https://www.ecma-international.org/publications/standards/Ecma-262.htm) - Ecma International (HTML,PDF)
 * [The JavaScript Tutorial](http://javascript.info) - Ilya Kantor (HTML)
-* [The JavaScript Way](https://github.com/bpesquet/thejsway) - Baptiste Pesquet (HTML)
+* [The JavaScript Way](https://github.com/bpesquet/thejsway) - Baptiste Pesquet
 * [The Problem with Native JavaScript APIs](https://www.oreilly.com/programming/free/native-javascript-apis.csp) - Nicholas C. Zakas (PDF, email address *requested*)
 * [Thinking in JavaScript](https://www.amazon.com/Thinking-JavaScript-Aravind-Shenoy-ebook/dp/B00JUI6LUQ) - Aravind Shenoy (Kindle)
 * [Understanding ECMAScript 6](https://leanpub.com/understandinges6/read) - Nicholas C. Zakas (HTML)