feat: expose more of KAPLAY's internals in exported context

[dragoncoder047]

I recently discovered the little ZzFX sound generator by @KilledByAPixel, so I thought I'd try to write a KAPLAY plugin to add it... Unfortunately there is one thing that gets in the way of writing a well-behaved ZzFX plugin.

The plugin would add a function loadZzFX(name, ZzFX parameters) to KAPLAY, and then monkey-patch play() to check the ZzFX sound-name-to-parameters mapping as well and call zzfx() if the sound name is registered there, otherwise defer to KAPLAY's original function. This all can be done as-is, but a step up from that (and what would probably be expected) would be to patch ZzFX as well so that it inserts its audio into KAPLAY's masterNode so that ZzFX sounds respond to volume() and get record()'ed, but I can't do that because the only thing that is exposed on the context in terms of the audio system is the AudioContext, not the masterNode.

So I'm kind of asking for this specific handle to get exposed, but I'm also kind of asking a general question of "what is the reasoning for exposing vs. not exposing certain bits of KAPLAY's internals?"

[lajbel]

We can back to export kaplay internals, we were doing that, for v4000 will be