Add audio input

[Chasyxx]

I can see Bytebeat's use as a modem (Here are FM and PSK modulators as proof of concept), but right now it can only serve as an audio output, making a demodulator pretty pointless, and making the signals that can be modulated rather limited. Even outside of modulation, I think an audio input has it's benefits (some sort of custom voice changer?).

Can there be a button or tickbox that activates an audio input (the button/toggle so the input isn't constantly activated, since it's usually a microphone)? I'm pretty sure all you'd need to do is pass an input sample as the third argument to a Funcbeat expression, 0 if it's off (or make it the 4th and have the sample number be the third since it's hard to go from seconds to sample index without imprecision, and what happens outside of funcbeat is further unknown, maybe a variable called dollchan_inputSample, _insample or something like that).