Add an external tutorial link of a complete game to wiki (#262)

* Add an external tutorial link of a complete game to wiki

Add a complete tutorial series for creating an 8-bit snake game from scratch

Author: rimmontrieu

wiki/articles/external-tutorials.md

@@ -16,6 +16,7 @@ These are webpages where individuals or companies write about their experience w
 - [Some blog posts regarding libGDX – by Rotating Canvas](https://rotatingcanvas.com/category/tutorials/)
 
 ### Complete tutorial series
+- [8-bit Retro Snake Game – 6 parts](https://raizensoft.com/tutorial/how-to-create-8-bit-retro-snake-libgdx/) (2025)
 - [GameDevelopment.blog – 17 parts](https://www.gamedevelopment.blog/full-libgdx-game-tutorial-flgt-home/) (2017)
 - [Flappy Bird Remake – 12 parts](https://web.archive.org/web/20140301152741/http://www.kilobolt.com/zombie-bird-tutorial-flappy-bird-remake.html) (2014)
 - [GameFromScratch.com – 17 parts](https://gamefromscratch.com/libgdx-tutorial-series/) (2014)