Document the ThirdReality Smart Button (3RSB22BZ) pairing mode quirk
that bit us today: the button has Standard ZigBee (blue only) and
Echo ZigBee (blue + red) modes, and only the former works with
zigbee2mqtt. Switching requires 5 quick presses of the back reset
button (firmware >= 1.00.22), NOT holding the front button.
Also document the Smart Plug Zigbee PROD pairing procedure and the
BLE->ZigBee mode switch.
