Support multilingual docs

[jverce]

Context

Recently, @Andygol took the initiative to translate the entire website (v3.5) to Ukrainian:
https://kubernetes.slack.com/archives/C3HD8ARJ5/p1736261563922009

In order to incorporate this work, we need to adjust the site's settings so that it handles multiple languages. This will initially involve splitting the language-specific configs into their own file. For example, taking the menu stuff from /config.yaml and put it in files like menus.en.yaml and menus.uk.yaml for English and Ukrainian, respectively.

[ivanvc]

Reference to Slack thread from @jberkus: https://kubernetes.slack.com/archives/C3HD8ARJ5/p1736815261935089

[jverce]

/assign

[jberkus]

Since this website has had some wonky history, do we want to make a feature branch for this?