* Add GPL-3.0-or-later license to 'Matters Computational' book entry
* Update free-programming-books-langs.md with new resources and licenses
* Add specific changes for second pull request
* Update books/free-programming-books-langs.md
Co-authored-by: Eric Hellman <eric@hellman.net>
* Added License in HTML book
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Co-authored-by: Eric Hellman <eric@hellman.net>
* [How To Build a Website with HTML](https://www.digitalocean.com/community/books/how-to-build-a-website-with-html-ebook) - Erin Glass (PDF, EPUB)
* [How To Build a Website with HTML](https://www.digitalocean.com/community/books/how-to-build-a-website-with-html-ebook) - Erin Glass (PDF, EPUB) (CC BY-NC-SA)
* [How to Code in HTML5 and CSS3](https://web.archive.org/web/20180816174417/http://howtocodeinhtml.com/HowToCodeInHTML5AndCSS3.pdf) - Damian Wielgosik (PDF) *(:card_file_box: archived)*
* [How to Code in HTML5 and CSS3](https://web.archive.org/web/20180816174417/http://howtocodeinhtml.com/HowToCodeInHTML5AndCSS3.pdf) - Damian Wielgosik (PDF) *(:card_file_box: archived)*
* [HTML Canvas Deep Dive](http://joshondesign.com/p/books/canvasdeepdive/toc.html) - Josh Marinacci
* [HTML Canvas Deep Dive](http://joshondesign.com/p/books/canvasdeepdive/toc.html) - Josh Marinacci