Documentation: Document how to use the Simulator

[keenanjohnson]

The micropython code has a great simulator mode that can be used to validate some functionality without the hardware. However, we don't have any documented instructions on how to use it. We should add those.

[keenanjohnson]

@damz perhaps you could add a few notes here on how you use the simulator when you develop? I can add them to the readme if so?