chore: complete creator and download links (#5532)

resource: "2D Game Development: From Zero To Hero"
section: books - english
Completes info about EbookFoundation/free-programming-books/#5528
as sugested by @Penaz91
in: https://github.com/EbookFoundation/free-programming-books/pull/5528#discussion_r706379597

books/free-programming-books.md

@@ -470,7 +470,7 @@
 
 #### Game Development
 
-* [2D Game Development: From Zero To Hero](https://github.com/Penaz91/2DGD_F0TH) (:construction: *in process*)
+* [2D Game Development: From Zero To Hero](https://github.com/Penaz91/2DGD_F0TH) - Daniele Penazzo (HTML, [PDF, EBPUB, Kindle...](https://therealpenaz91.itch.io/2dgd-f0th#download)) (:construction: *in process*)
 * [Coding With Minecraft](https://turtleappstore.com/book/) - Al Sweigart
 * [Designing Virtual Worlds](https://mud.co.uk/richard/DesigningVirtualWorlds.pdf) - Richard A. Bartle (PDF)
 * [Game AI Pro](http://www.gameaipro.com) - Steve Rabin