Add example sketch for finding/debugging the correct audio devices

[kevinstadler]

Since finding the correct audio device is such a common task (which often involves repeated guessing thanks to uninformative device names), it could be useful to have a 'Debug' example sketch which simply 1) plays back a sine wave and 2) shows the waveform of the current AudioIn, where the user can simply cycle through all available audio devices by clicking the mouse. Information on the currently selected devices should also be displayed on the screen.

[dhowe]

A simple selector component (like a dropdown that lets a user pick a device) would be super useful