[MicroPython Feature Request] UF2 to wipe main.py

[menehune23]

A UF2 (and accompanying documentation) that resets/wipes the main.py from the filesystem would be super useful to help when a user has gotten their code into a bad state. The other day, my son had errors in his code and couldn't reconnect to Thonny.

Perhaps even better is to detect a key combo on boot and wipe the main.py if that occurs, to unbrick it. Then the user wouldn't need to go through and install a separate UF2 and reinstall the official one.

[menehune23]

Heads up, I'm working on this over in my fork: menehune23#2

Will PR to this repo once it's working. I'm pretty new to MicroPython, so if you have some time to take a peek at that PR and offer any comments, I'd appreciate it!