Release v1.3.1 on 2021-02-28.

1. 3b8f7c4 Add a (hidden) VTY parameter for Rx/Tx freq. shifting by Vadim Yanitskiy · 6 years ago
2. e91544d Calculate RSSI offset based on RxGain configuration by Pau Espin Pedrol · 3 years, 8 months ago
3. 93fee1f Transceiver: Pass config struct instead of large list of params by Pau Espin Pedrol · 3 years, 8 months ago
4. efac20b Move enums required by VTY to a separate header by Pau Espin Pedrol · 6 years ago