LibreTranslate custom instance

[Collide]

At present the API of LibreTranslate in its own instance does not work, it would be good that you can choose other instances or some custom from the configuration panel :).

[PalmerAL]

The default instance should be working again, sorry about that!

I think it's unlikely that very many people would have an alternative instance to use, but it's pretty easy to swap out the URL and then recompile: https://github.com/minbrowser/min/blob/master/js/pageTranslations.js#L6

I'm hoping we can switch to Bergamot pretty soon; the translation quality seems a bit better, and it can run entirely locally (so faster, more private, and I don't have to keep paying for a server). They don't support as many languages yet, but they're getting closer: https://github.com/mozilla/firefox-translations-models