Add translation keys for RMV Departures plugin

As suggested by Mario, I would like to add these keys to the translations for custom_plugins:

**de**
`time`: Zeit
`direction`: Richtung
`line`: Linie
`delay`: Verspätung
`on_time`: pünktlich

**en**
`time`: Time
`direction`: Direction
`line`: Line
`delay`: Delay
`on_time`: on time
