Implement music beat detection

[BaptisteHudyma]

Now that the sound modes are back, and the FFT is correct, the beat detection should be added back.

The original beat detection was based only on sound intensity, and that is dumb.
The new beat detection shall use the fft results and infer a beat detection result per fft bins.
This will allow modes to choose a base beat frequency, and make for more options.

Here is a link to an implementation close to the desired on