Add callback for muxed buttons using 47165

[serlecu]

Following the issue https://github.com/luni64/EncoderTool/issues/31#issuecomment-1478023327, I've implemented the callback for muxed buttons for the 47165 IC, analogous to encoders.attachCallback(onAnyEncoder);.

I tested it successfully on a teensy++ 2.0 and following the schematics provided in the docs of this repo.

[serlecu]

OK, sorry, I just noticed that I didn't revert my first commit...