[Feature request]: add a pure black theme option.

[ghost]

I would appreciate a pure black/oled/amoled theme and an option to set accent color. Love the app, thanks for developing and sharing it.

[1RandomDev]

I'm currently not planning on adding new features to my fork except for the ones necessary to remove trackers. But it looks like there's already an open issue in the upstream repository (https://github.com/michaldrabik/showly-2.0/issues/607) and if it gets implemented there I will of course merge it into my fork in the next release.