Add board support for Seeed XIAO ESP32C6

[LynnL4]

FYI https://github.com/espressif/arduino-esp32/pull/9330 https://wiki.seeedstudio.com/XIAO_ESP32C6_Getting_Started/

[lboue]

Could you validate this request?

[mnowak32]

Kinda confirmed - I've got it to work in PIO/VSC with following measures:

• forked @LynnL4 repo and merged newest changes from upstream,
• added the newest (as for now) version (3.0.2) of arduino-esp32 framework to platformio.ini - without this change there were errors regarding missing SConscript:

  [env:seeed_xiao_esp32c6]
  platform = https://github.com/mnowak32/platform-espressif32.git#boards/seeed_xiao_esp32c6
  platform_packages = 
  framework-arduinoespressif32 @ https://github.com/espressif/arduino-esp32.git#3.0.2
  framework-arduinoespressif32-libs @ https://github.com/espressif/arduino-esp32/releases/download/3.0.2/esp32-arduino-libs-3.0.2.zip
  framework = arduino
  board = seeed_xiao_esp32c6

The project I've used depends on libs like mmwave_for_XIAO, EspSoftwareSerial and NeoPixelBus, all working flawlessly.