[Library Manager] Please add IwitVolumeKnob library

[M-Reimer]

I've created some library which allows to support some "chinese volume knob device" with own software:

https://github.com/M-Reimer/IwitVolumeKnob

It depends on my "EncoderStepCounter" which would have to be added to the library manager, first:

#9247

[cmaglie]

done