I added the ability to use setGain() on AudioInputPDM

[gitcnd]

Hi Paul - I added a feature to your already-awesome PDM code :-)

I'm working to live-stream binaural 3D-stereo underwater whale-songs to youtube, and those are rather quiet (from where I am setup, near shore, in wifi range), so I needed some gain control.

I'm using SiSonic SPH0641LU4H-1 MEMS PDM Microphones, which your code works nicely with. These are also capable ultrasonic (80-khz) devices; if I get really sidetracked, I might mess about with additional sample-rate code adjustments...