Darkmode

[Gkiokan]

• [x] Prepare Darkmode Options in Settings
• [x] Add sync handler
• [x] Add Darkmode CSS

[Gkiokan]

Base implementation is done. Figuring out a nice color schema now. Maybe there will be more then light and darkmode. Maybe a rainbow style, too.

[Gkiokan]

Further progress

[Gkiokan]

DARKMODE is out now. Available from the v2.6.0-pre-release.