List Raspberry Pi Pico as supported

[functionpointer]

This library is based on arduino, and there are arduino cores for RP2040. So it should be listed as supported.

I have tested it using ESPHome, it compiles just fine and sends stuff over uart. Test with real air conditioner is pending.

external_components:
  - source:
      type: git
      url: https://github.com/functionpointer/esphome
      ref: lampe
    components: [ midea ]
    refresh: 1h