Introduce bot/site translations

[mark-ignacio]

Community-contributed zh-Hant translations were in use with v1.

Probably good to use gotext or perhaps one of the cloud-based platforms that people are used to, like Crowdin or Transifex.

https://www.alexedwards.net/blog/i18n-managing-translations
https://free-for.dev/#/?id=translation-management

[DaniruKun]

It's also possible to just use formatted Google Sheets, and then create an importer for them using a sheets client lib. I think LiveTL guys use the same approach, and we also do the same at Platogo for dozens of languages and keys.