Status indication via RGB LED:
Cycle RGB = Boot, Flashing Green = Awaiting connection, Flashing Blue = Connecting, Solid Blue = Connected (R = Pin 19, G = Pin 18, B = Pin 23)
Push Button toggles hibernation/wakeup (Pin 27, internal pulldown)
A2DPSink: https://github.com/pschatzmann/ESP32-A2DP
