Add support for multiple languages / localization via external language files

[chebunindmitry]

Hello and thank you for your great work on OneTagger — it's a very useful tool!

I would like to ask if you would consider adding support for multiple languages (i18n), or at least making it easier for users to translate the UI by using external language files.

Currently, the application appears to be English-only. Supporting localization would allow non-English-speaking users to better use the app, and the community could help contribute translations (for example, via simple JSON files in a locales folder).

Even just a basic implementation that allows switching between available language files would be a great start.

Would this be something you'd be open to including in a future release? If so, I'd be happy to contribute a translation for Russian.

Thanks again for the great tool!