Add support for other display frameworks

[thijstriemstra]

Currently the base emulator class imports pygame and all other subclasses thus use pygame as well. It would be nice to add different emulators, eg. a PyQt5 one, meaning the base emulator shouldn't rely on pygame.

[rm-hull]

I think the base emulator uses pygame surfaces to do the scaling and transforms

[thijstriemstra]

See https://pillow.readthedocs.io/en/stable/reference/ImageQt.html