Documentation for StereoEnhance audio effect

[jambonsupreme]

Your Godot version:

3.4.4

Issue description:

The description for the StereoEnhance effect states: "This effect uses a few algorithms to enhance a signal's stereo spectrum". I don't think this explains very well what it does (what algorithms? enhance how?). Also none of the properties (pan_pullout, time_pullout_ms and surround) are documented.

URL to the documentation page (if already existing):

stable https://docs.godotengine.org/en/stable/tutorials/audio/audio_buses.html latest https://docs.godotengine.org/en/latest/tutorials/audio/audio_effects.html

[Calinou]

cc @ellenhp