New DEMO ending + tweaks

This update touches on several things ingame.

1. Fixed several bugs, notably the path of will o' wisps.
2. Changed the DEMO's ending, good luck getting there, but the payoff is worth it (kinda?).
3. Added several animations + an unused scene for a future roguelike mode, currently WIP.
4. Changed the starting menu. Originally you opened the game and then you were presented an image that corrupts itself when pressing on a button. Now there's a proper starting screen. Courtesy of Vinesauce's Link between world's corruption stockpile for the background.
5. Added a mouse icon to replace your desktop mouse. I want this game to feel authentic!

Hope you'll enjoy this update!