Document localized footer and navbar for multi-language sites

[mintlify]

Summary

• Added documentation for language-specific footer and navbar configurations in multi-language sites
• Updated the Languages section in navigation docs with example showing localized footer and navbar
• Added footer and navbar ResponseFields to the languages array schema in settings reference
• Added new Localized footer and navbar section to the internationalization guide

These updates reflect the new feature that allows configuring different footer links and navbar content per language.

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Note

Low Risk
Documentation-only changes (examples and schema reference text) with no runtime/code-path impact.

Overview
Adds documentation explaining that each navigation.languages[] entry can override global UI chrome via language-specific footer and navbar (and similarly banner).

Updates the internationalization guide with a new "Localized footer and navbar" section and example docs.json, refreshes the navigation guide language section and example to include these fields, and extends the docs.json settings reference for navigation.languages to list banner, footer, and navbar as supported per-language properties; also corrects the Ukrainian language code from ua to uk in the i18n guide.

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