Replace rpi-led-matrix with something that isnt GPL

[TheButlah]

GPL smh

[TheButlah]

I found hub75. Not only is this permissively licensed, its pure rust so there is not clunky c++ build step. Also, it uses embedded-graphics which means you should be able to use several really nice crates to make drawing easy.

If you still want to use a c++ library, the official adafruit one is BSD licensed.

[TheButlah]

It actually looks like both hub75 and the rpi-led-matrix crates both use embedded-graphics. So you could base the code around those traits and make it not care what the backend is.