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)
It wasn't copying the frame data from the sources to the output frame
correctly, and there was a small period of zeros at the start of the
frame.
I also converted to using a vec of tuples for the two channels to
make it easier to reason about, since some of the issues were related
to the differences sizes calculated from the clock based on the sample
rate
I wanted to make this a bit more modular, so it's easier in theory to
write external crates that can reuse bits, and selectively compile in
bits, such as adding new systems or new cpu implementations
