LoRa/LoRaWAN support for RAK11300/RAK11310 (RP2040 + SX1262 LoRa transceiver)

[beegee-tokyo]

Still in testing, I ported the SX126x-Arduino library to work with the Arduino-Pico BSP for the RAK11300 module.
The RAK11300/RAK11310 is a RP2040 combined with a Semtech SX126s LoRa transceiver. Library link SX126x-Arduino

The functionality is not yet published to Arduino and PIO library managers, but you can install and test it manually the usual ways.

On ArduinoIDE, the usual way with installation from ZIP file.
On PIO by using

lib_deps = 
	https://github.com/beegee-tokyo/SX126x-Arduino.git
	khoih-prog/RPI_PICO_TimerInterrupt

in platformio.ini.

Feedback is welcome and helpful.

I want to thank @earlephilhower for providing the Arduino Pico BSP. With plain FreeRTOS support it was quite easy to get the library up and running.

[beegee-tokyo]

Fixed some timer problems. Still testing, but it seems to work now.