What's the problem this feature will solve?
Relay visual feedback of heading for debugging and verification.

Describe the solution you'd like
It'd be nice to be able to load in an image of the agent and rotate it based on the heading. For example, in the continous space, if a boid flocker is moving at a 45 degree angle, instead of the red dot, an image of a bird could be loaded which is facing at the 45 degree angle.

Additional context
This is primarily working with the boid flocker example in the mesa/examples directory.