Added button for darkmode in Studio (on settings-page).
Studio also detects OS preference (auto-detection) and launches studio in dark- or lightmode.

NOT tested with MacOS

Auto-detection does not work with Chrome and Chromium on Fedora 35, this seems to be a bug.

Fixed typo

- header has now correct color on initial loading
- when recording the header overlay is now darker in darkmode
- error messages: text now white/light in darkmode
- removed accidentally added whitepaces (my IDE had "format on save" active)
- other minor things [e.g. removed accidentally added whitepaces (my IDE had "format on save" active)]

- removed button for darkmode and added a dropdowm instead
- updated theme-ui to v0.14.5 this closes elan-ev#812
- added some config -> this plus update fixes bug with auto preference for darkmode
- some color adjustments, also removed some unused colors from theme.js
- moved css for tooltip and tab-navigation to theme.js (they now use color variables)

- Studio was always choosing system-preference over localstorage, so if the user set Studio to darkmode but system is in lightmode, on refresh Studio was always using lightmode
- So now: on initial load Studio uses system-preference (if nothing stored to localstorage) otherwise Studio uses localstorage

- changed the focus-colors for tab-navigation for better contrast in light and darkmode
- focus-outline for recording buttons now round

- changed outline-color for video-settings to green for better visibility
- aligned outline on recording-buttons

System preference should now work. After OS preferences have been changed, the page must be reloaded to see the change in Studio.

- removed unused package
- indented a few lines