Draft: [Infra] Integrate with KDE Localization Workflow

Changelog

• Introduced xliff2po.py and po2xliff.py for converting between XLIFF (format that Xcode uses) and po/pot (format that the translation team uses)
• Added StaticMessages.sh for exporting and importing translations
  • requires xcodebuild to be present and working -- so Scripty probably needs to run on macOS

Future Directions

• Support plurals as in https://developer.apple.com/wwdc23/10155, or stringsdict

Alternatives Considered

xliff2po/po2xliff

• https://github.com/translate/translate works for generic XLIFF and gettext files, but doesn't quite work with XLIFF from Xcode
• https://localise.biz/free/converter/ios is closer, but changes the localized string keys to wrong ones

gettext instead of Text/NSLocalizedString

• https://github.com/hulab/POLocalizedString: I strongly prefer us to stick with the SwiftUI paradigm as close as possible, so unless there are compelling reasons otherwise