Dark theme based on system default

[stefan-niedermann]

It was awesome if one wouldn't need to switch the theme of the app manually to dark or light but could just choose system default, so the app automatically uses either the dark or light theme based on the system preference.

Two personal annotations which are not necessarily relevant for all people:

1. Actually I personally would not even need dark or light settings, but as an app developer, I know how sustained users are if you woul even try to remove an existing feature 😆
2. My Android device toggles between dark and light system theme depending on sunset / sunrise automatically. Adjusting the apps manually is therefore especially "hard work" in my case 😉

[julianfairfax]

Yes this would be nice