i18n for notices

[staltz]

Context: https://github.com/ssb-ngi-pointer/go-ssb-room/pull/40#issuecomment-785827717

• The notice page (e.g. Code of Conduct) would automatically pick up the user's declared browser language
  • See also the currently hard-coded en-GB for complete:index route, which also needs to detect the language
  • See also the hard-coded en-GB in the template function urlToNotice
• The notice page would show links to alternative translations if they exist You can see how this is done in web/i18n - once we do this proper we need to consolidate this with the user session maybe but copying that and just using accept-language should be fine for now. tangential: We also need a list of languages and flags somewhere

[staltz]

@cblgh @cryptix What do you think about this old issue? Is it done?

About the second bullet item, maybe we don't need to do it now that there is the language selector.

[cryptix]

urlToNotice still needs to be fixed to not use the hardcoded language.