UI update timer/interval

[WeirdConstructor]

For HexoSynth I need something that polls the audio backend regularily (at 60 fps)
to update the visual feedback in the GUI (LEDs, signal graphs, ...).

For this I either need something like an on_frame function on the Widget, which could be enabled on demand when building builder.set_receive_frame_updates().

Alternatively any other mechanism that gives me this somehow will suffice of course. For instance an interval timer I can set to 16.6666667ms. Ideally it would be vsynced or something like that, like with baseview, because I guess only then I can make a smooth scrolling signal waveform?

[geom3trik]

Related issue #23