create perks system

[azhou202]

possibly create objects to shoot that grant perks such as shield, increased ship speed, more bullets, extra life, larger bullets, or pass-through bullets

[azhou202]

perks features

• shield
  protect against three crashes
  icon should be a shield
  when shielded ship should have an outline, or screen should have message saying shield is active and saying shield strength

• super lasers
  should last for 20s
  icon can be big bullet
  extra wide and can pass through aliens

• extra ship
  icon is just a ship
  adds an extra ship but cannot go above max ships allowed

• should randomly generate and move like an alien ship but not cause issues if crash into ship or go off screen