Post-jam difficulty update

This isn't going to be the only update, but for easy of accessibility I wanted to add it.

What's new:

• Difficulty can now be selected, with a total of 3 difficulties: Easy, Normal, and Hard

What will be added at a later stage (This is subject to change):

• More layouts, the Hard mode having it's own, larger layouts
• New tools for the player to use
• Abilities, such as a dash
• Juice
• Different colour palettes