[Feature request] System theme

There is already Dark theme, Light theme, but there should be 3. option - System theme - that just follows whatever the system theme is. And it should be the defaut option.

Reasons
1. I dont want to change themes in all my apps, if I want to change theme, I change theme of my device
2. On first opening I want to see system theme - default theme is right now light theme - there is reason if I set dark theme as my system theme