The LoRa and LoRaWAN documentation was not included anywhere, so the
Doxygen comments in drivers/lora.h and lorawan/lorawan.h were not
rendered. This commit adds a new section for LoRa and LoRaWAN to the
documentation.
People often confuse the difference between LoRa and LoRaWAN, so it
makes sense to combine both in the same doc section.
LoRa would otherwise not fit very well into any docs category, as it
is a driver, but not really a peripheral.
Signed-off-by: Martin Jäger <martin@libre.solar>