Upgrade system and Polish

I added an upgrade bubble that emits grenn light, when you collect you get an random upgrade. Got these upgrades: grappling speed, beam damage, shoot speed, shoot damage, max air and shooting while grappling.

I also made an icon for the game, balanced it and improved the dynamic music.

There is linux build now but couldn't tested it.

Also a funny little accident that happened is that I tried to upload this update without like any internet on vacation and somehow managed to delete previous game files from itch, so you couldn't download the game and I was wondering why I didn't got any downloads.

Feedback is appreciated. Have a nice day.