Added JavaScript, PHP, Go and Swift books (#7382)

* Added multiple books from Flavio Copes

Added books covering PHP, JavaScript, Go and iOS (Swift).

* Fixed alphabetical order

Fixed alphabetical order by placing the new elements in the correct spots.

* fix: use HTML instead of Online

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

books/free-programming-books-langs.md

@@ -430,6 +430,7 @@ That section got so big, we decided to split it into its own file, the [BY SUBJE
 * [Build Your Own Lisp](http://www.buildyourownlisp.com) - Daniel Holden
 * [C Elements of Style](http://www.oualline.com/books.free/style/) - Steve Oualline
 * [C for Python Programmers](http://www.cburch.com/books/cpy/) - Carl Burch
+* [C Handbook](https://thevalleyofcode.com/c/) - Flavio Copes (HTML, PDF)
 * [C Internals](https://www.avabodh.com/cin/cin.html) - Rajeev Kumar (HTML)
 * [C Notes for Professionals](https://goalkicker.com/CBook) - Compiled from StackOverflow Documentation (PDF)
 * [C Programming](https://en.wikibooks.org/wiki/Programming%3AC) - Wikibooks
@@ -791,6 +792,7 @@ That section got so big, we decided to split it into its own file, the [BY SUBJE
 * [Go by Example](https://gobyexample.com)
 * [Go for Javascript Developers](https://github.com/bulim/go-for-javascript-developers)
 * [Go for Python Programmers](https://golang-for-python-programmers.readthedocs.io/en/latest) - Jason McVetta (HTML, PDF, EPUB)
+* [Go Handbook](https://thevalleyofcode.com/go/) - Flavio Copes (HTML, PDF)
 * [Go Succinctly](https://www.syncfusion.com/succinctly-free-ebooks/go-succinctly) - Mark Lewin (PDF, EPUB, Kindle)
 * [Go Tutorial](http://www.tutorialspoint.com/go/) - Tutorials Point (HTML, PDF)
 * [Go Web Development Succinctly](https://www.syncfusion.com/succinctly-free-ebooks/go-web-development) - Mark Lewin (PDF, EPUB, Kindle)
@@ -1088,6 +1090,7 @@ That section got so big, we decided to split it into its own file, the [BY SUBJE
 * [JavaScript from ES5 to ESNext](https://flaviocopes.com/page/es5-to-esnext/) - Flavio Copes (PDF, EPUB, Kindle) *(email address requested)*
 * [JavaScript Fundamentals, Plus a Dash Of JQuery - for dinner ladies](http://nicholasjohnson.com/javascript-book/) - Nicholas Johnson (HTML)
 * [JavaScript Garden](http://bonsaiden.github.io/JavaScript-Garden/) - Tim Ruffles (HTML)
+* [JavaScript Handbook](https://thevalleyofcode.com/js/) - Flavio Copes (HTML, PDF)
 * [JavaScript Interview #35](https://gumroad.com/l/javascript-interview-35) - Coderslang Master (PDF, email address *requested*, not required)
 * [JavaScript Notes for Professionals](https://goalkicker.com/JavaScriptBook/) - Compiled from StackOverflow documentation (PDF)
 * [JavaScript Patterns Collection](http://shichuan.github.io/javascript-patterns/) - Shi Chuan (HTML)
@@ -1698,6 +1701,7 @@ That section got so big, we decided to split it into its own file, the [BY SUBJE
 * [PHP Apprentice](https://phpapprentice.com) - Andrew Davis *(:construction: in process)*
 * [PHP Best Practices](https://phpbestpractices.org)
 * [PHP Documentor - Documentation](https://docs.phpdoc.org) - phpdoc.org
+* [PHP Handbook](https://thevalleyofcode.com/php/) - Flavio Copes (HTML, PDF)
 * [PHP Internals Book](http://www.phpinternalsbook.com)
 * [PHP Notes for Professionals](https://goalkicker.com/PHPBook/) - Compiled from StackOverflow Documentation (PDF)
 * [PHP Pandas](http://daylerees.com/php-pandas/) - Dayle Rees
@@ -2334,6 +2338,7 @@ That section got so big, we decided to split it into its own file, the [BY SUBJE
 
 * [Essential Swift](https://www.programming-books.io/essential/swift/) - Krzysztof Kowalczyk (Compiled from StackOverflow Documentation)
 * [Hacking with Swift](https://www.hackingwithswift.com)
+* [Swift Handbook](https://thevalleyofcode.com/swift/) - Flavio Copes (HTML, PDF)
 * [Swift Notes for Professionals](https://goalkicker.com/SwiftBook/) - Compiled from StackOverflow Documentation (PDF)
 * [The Swift Programming Language](https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/Swift_Programming_Language/index.html) (HTML) [(iBook)](https://itunes.apple.com/us/book/swift-programming-language/id881256329?mt=11)
 * [Using Swift with Cocoa and Objective-C](https://developer.apple.com/library/content//documentation/Swift/Conceptual/BuildingCocoaApps/index.html) (HTML) [(iBook)](https://itunes.apple.com/us/book/using-swift-cocoa-objective/id888894773?mt=11)