Auto dark theme on Android

[jjrpayne]

An option to auto-select the dark theme based on the user's system settings would be a nice feature.

[mimoguz]

Hi. I'm not sure if libgdx has an api for querying system theme, but I can add this to my to-do list for my rewrite, that is unfortunately long interrupted due to multiple consecutive health issues. I'll need to redesign the options dialog anyway.

[jjrpayne]

I'd be interested in implementing this if I may contribute. I imagine it should be possible to pass the system theme through the Android launcher if an API query doesn't exist.