add How to Code in HTML5 and CSS3 to free-programming-books.md (#2038)

* Update free-programming-books.md

add How to Code in HTML5 and CSS3

* Update free-programming-books.md

* Update free-programming-books.md

free-programming-books.md

@@ -1172,6 +1172,7 @@
 * [Dive Into HTML5](http://diveintohtml5.info) - Mark Pilgrim ([PDF](http://mislav.net/2011/10/dive-into-html5/))
 * [GA Dash](https://dash.generalassemb.ly)
 * [Google's HTML/CSS Style Guide](http://google-styleguide.googlecode.com/svn/trunk/htmlcssguide.xml)
+* [How to Code in HTML5 and CSS3](http://howtocodeinhtml.com)
 * [HTML Canvas Deep Dive](http://joshondesign.com/p/books/canvasdeepdive/toc.html) - Josh Marinacci
 * [HTML Dog Tutorials](http://www.htmldog.com)
 * [HTML5 Canvas](http://chimera.labs.oreilly.com/books/1234000001654/index.html) - Steve Fulton & Jeff Fulton