perf: disconnect our `AudioWorkletNode`s when `volumeThreshold === 0`

[WofWca]

Although it's not particularly common for people to use the extension this way, would be nice to have. This will reduce CPU load and (maybe) reduce the likelihood of glitches occurring (see https://github.com/WofWca/jumpcutter/issues/24#issuecomment-906853984)

https://github.com/WofWca/jumpcutter/blob/d81da1596a2dfa89a35bbc7b0cb0d28880f6f2e2/src/entry-points/content/StretchingController/StretchingController.ts#L281