Article internationalization

[elegaanz]

Is your feature request related to a problem? Please describe.

The same article may be available in multiple languages.

Describe the solution you'd like

Add a way to publish the same article in various languages. There should a language switcher on the reading page, and maybe a banner with a link to the translated version if you are not reading the article in your "favorite" language while it is available.

Describe alternatives you've considered

Manually publishing different versions of an article and linking them together. It works but it is more work.

~~Additional context~~