Improve enemy animation

[kendallroth]

Enemies should utilize several animations over their lifecycle:

• Create custom component to handle animation
• Scale up while spawning (from nothing)
• Transform/rotate enemies slightly to simulate motion
• Scale down when exiting at destination
  • Maybe base this on distance to exit waypoint?

Enemies should have their exit animation sometime before being destroyed at the exit, in order to give a satisfactory animation time. However, a life should not be substracted until they have fully "reached" the destination (inside tower).