Improved game a lot

I didn't like that the game was full of glitches and still lacked fundamental features, so I kept working on it...

Here's what's new:

• Increased dungeon size to 6x6
• add 2 new Hard enemy slimes
• fixed a ton of glitches (there are probably a ton left lol)
• game now gets harder over time: more slimes spawn and slime enemy difficulty increases
• improved main menu + added music
• added win condition and a goal to the game
• added a cute purple slime to talk to
• improved player model with a hat
• improved crate
• fixed up some rooms