Add art for upgrades

[FelixEder]

The upgrades now only have temporary designs, make them all into nice pixelart. This should also include the drops enemies makes as well as health/energy permanent upgrades. Have specific sprites for each of these.

These are the specific upgrades that need art:

• [x] Float

• [ ] SecondJump

• [ ] Walljump

• [ ] Stomp

• [x] MegaPunch

• [ ] SmallFry

• [ ] Health Upgrade

• [ ] Energy Upgrade

[FelixEder]

The design of the upgrades (except laster-shooter) should be a symbol that represents the power-up.