Move the LED control to the utils.LedManager class. For the first
implementation, support two LED patterns 'idle' and 'playing'.
Extend the PlayerApp to set the LED pattern based on playback state.
Signed-off-by: Matthias Blankertz <matthias@blankertz.org>
Make mypy run with proper type stubs for micropython RP2.
Add basic structure for pytest testing.
Signed-off-by: Matthias Blankertz <matthias@blankertz.org>
