Play note(s) on user input

[rvictorino]

as seen here: https://dev.to/sustained/comment/f650

A nice and useful feature would be the support of user inputs to play sounds.

Considered inputs are:

• MIDI piano
• computer keyboard
• the UI keyboard (clicking on the visual keys)

My 2 cents on the computer keyboard: A really good feature that is yet to be found on any web-based virtual piano is the ability to configure key mapping: each keyboard is different, in size, shape and layout. Some default mapping for qwertys is good, customizable mapping is great.