Settings persistence and allow changing language

Also partly covers #196 (closed) by introducing a Settings interface where all settings are to be managed, but I didn't integrate those yet with the FeatureFlags, nor did I provide them via LocalCompositionProvider since it is not needed for the two settings we are currently supporting. If you think it's a good idea, I could certainly add another commit where I fully address #196 (closed) as well.

Closes #212 (closed)

changed milestone to %Desktop 0.2.0

added S: in progress Sponsor 7 labels

added 4 commits

• 7df90415 - 1 commit from branch main
• 8baee3bd - make theme setting persistent
• e001aacc - use select instead of switch for theme setting to allow for system default
• 2a71257c - add persistent language setting

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added 1 commit

• f06b9ece - update instructions in TRANSLATION.md

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Just added a bugfix for the chinese locale (which is the only one with a country code). Should be ready for review now!

mentioned in merge request !132 (merged)

Not sure how this can be done easily, but I think it would be best if each language was displayed in the language's language. I.e. if English is my current language instead of displaying "English, German, Spanish", it would be "English, Deutsch, Espanol"

added requires-translations label

mentioned in merge request !155 (closed)