Rpgpy

- Raise RPGFileError if file reading fails

- Support Python 3.11

- Fix numpy warnings
- Change velocity vectors to ordinary numpy array

- Add support for RPG version 1 files
- Change RPG file version 3 to 3.5
- Write `rpg_file_version` attribute to netCDF output
- Add py.typed to enable type checking

- Fix mask in `decode_rpg_status_flags`

- Add `decode_rpg_status_flags` function
- Add `rpg_seconds2datetime64` to quickly convert array of timestamps