ZombieShrooms mini-boss

Added a mini-boss to the game. Here is the process of working on it.
Links to previous posts on the game:
https://www.artstation.com/artwork/YG25A6?album_id=14492745
https://www.artstation.com/artwork/V2v9kn?album_id=14492745
https://www.artstation.com/artwork/OvKZ98?album_id=14492745
https://www.artstation.com/artwork/YGvvQw?album_id=14492745