## Link to GitHub Issue or related Pull Request, if one exists
n/a
## Description of change
Touch piano mode. Allows piano keys to be played with the touch screen.
Since the touch screen is still needed for menu navigation (including
during songs) a toggle switch is added so that the user can flip between
navigation mode and piano mode.
The touch targets are pixel-perfect. Don't let the game's piano
animations fool you.
## Testing
bicarus