Allow to change language for UI

[twoco]

What problem does this feature solve?

Currently you see the app in the language of your browser. It's good as default value, but for dev related stuff I want english.

What does the proposed API look like?

Currently there is a language icon in the bottom right. I would provide a menu to on click to select the prefered language and keep the "improve translation" in that menu. Remember that choice (localStorage).

Alternative temporary solution: We could read vue-ui-language in local storage like we already have for vue-ui-dark-mode. I could set it via JS (dev tools) to en.

I don't want to change the language of my browser. I just prefer english for dev stuff but keep all other pages in my native langauge. We could also just toggle between auto (from browser) and en.