Audio driver for buzzer

[tomvanbraeckel]

Here's my audio driver for the piezoelectric buzzer of the Fri3D Camp 2022 badge!

There is quite some code so I opted to put it in separate files, to keep rg_audio.c manageable.

The general working principle is described in rg_audio_buzzer.c

Audio quality is not too bad, for a buzzer.

There might be some tweaks or brilliant methods of improving the quality further, but I think this simple driver is a good baseline, with sensible, understandable parameters.