convert locales from a session/cookie to individual directories

[recluse4615]

when working with multilingual sites, it's generally recommended for SEO purposes to:

• define the language inside the markup
• include the language/locale in the url (eg: https://content.minetest.net/en-us/ vs https://content.minetest.net/)
• (optionally - need to confirm) use hreflang on canonical urls to denote different translated versions of the page

problems:

• package pages: UGC is not translated in to multiple languages, how can we deal with this?
• flat pages: these also aren't translated

this might be something that's either impossible to do or very difficult, but would be ideal in the long term

[rubenwardy]

This requires package meta translation, which requires that the engine support it first ( https://github.com/minetest/minetest/pull/12208 )

[rubenwardy]

Engine support has been merged, which means that this issue is now waiting on #516

[rubenwardy]

closing for now, this would be quite disruptive for such a low % of translated packages. Can be reconsidered when more packages support translation