The debug loop that reads a command and does something is part of the
frontend's main loop, so that it can potentially update, even though
it doesn't actually work for minifb because the command input is a
blocking call. It's also not implemented in the pixels frontend.
At some point I'll make a web frontend.
It now actually checks the clock and tries to mix the audio in sync
relative to the clock, but the cpal output doesn't yet try to sync
to the StreamInstant time. Sound seems a lot better on chrome in
wasm, but and kind of better on firefox despite frame skipping not
being supported yet, but it's way slower for some reason (12fps)