[i18n] Make Xcode export all user interface strings for localization

Changelog

• Enabled "Use Compiler to Extract Swift Strings" (SWIFT_EMIT_LOC_STRINGS) in build settings
• Contributors.json is replaced by Contributors.swift so it's easier for us to implement !67
• Internationalize ColorScheme (app theme) picking UI
• Added NSLocalizedString to parts of the program that's missing it
• Fixed typos and unified spellings

Example XLIFF

en.xliff

Detours

I was initially misguided by Preparing Views for Localization saying that "Xcode doesn’t parse these views [other than Text] for localization, you need to manually add the localization strings." The code that switch all LocalizedStringKey to Text can be found at https://invent.kde.org/apollozhu/kdeconnect-ios/-/commits/work/localization/xcodebuild-exportLocalizations-backup, and it produced en.xliff.