Add Resampling

[nicschumann]

Not all browsers allow you to set the sample-rate on device. The main issue is Firefox, which vomits when you ask it to set the sample-rate of the AudioContext to anything other than the hardware sample-rate of the microphone. There are multiple options for dealing with this:

• Build an AudioWorklet node which implements a resampling transform from the native sample-rate (probably 44.1kHz or 96kHz) to the target sample rate of 8kHz. This is nice because it leverages resampling off of the browser's main thread.
• Move the resampling to WASM and leverage a resampling library that implements the resampling transform natively. There's a compelling library option called Rubato, and given the low over-head of our WASM right now, this probably wouldn't be too bad.
• Don't support Firefox. There's basically nothing good about this option.

[nicschumann]

Leaning towards the 2nd bullet point above. It's the most compatible with the layout of the library, and keeps this thing "drag and drop": all functionality will still be accessible through a single setup call to .init() and a single usage call to .analyze(x : Float32Array).