* added C Programming Language book PDF source

with reference to issues [3189](https://github.com/EbookFoundation/free-programming-books/issues/3189)
Added C Programming current standard PDF source.

* Add PDF indication

* Update deprecated links to Google's Android courses

* Renaming link to codelab in alphabetical order

* Rearrange in alphabetical order

* Remove Android Developer Fundamentals from books

* Add Android Developer Fundamentals to courses list

* Adding Harvard GSE Scratch Book

* adding raspberry pi press book

* spelling sorting doesn't ignore "an" as first word of title

* add introduction to Ada course book

* Change book to add

Add Ada for the C++ or Java Developer book instead.

* add author name to an ada book

* Update free-programming-books.md

* Add a new Ada section

* Update free-programming-interactive-tutorials-en.md

Course is depreciated

* Add Intro to JavaScript ES6 programming

* fix lint

* fix lint

* fix introducing to es6 to playlist link

* add GitHowTo

* fix lint

* adding 5 Chinese documents for Python.

* Sorry for the spelling mistake.

* Update free-programming-books.md

* Update free-programming-books.md

Sorry for the error, fixed the spaces so that the linting will now work.