Android version, new enemy

This is a post-jam update with many improvements!

• an Android version was added
• new enemy type - a huge jumping slime
• the labyrinth is now bigger and only has one exit
• snakes are smarter
• many sounds, particle effects and, of course, a lot of screenshake was added
• the entire game was ported to Unity - sadly I couldn't get Godot to achieve the kind of web performance I wanted
• performance vastly improved in all versions