Add Spanish localization support to Openverse

[yashhhYB]

Fixes

Description

• Added Spanish language file (es.json).
• Updated supported locales to include Spanish.
• Implemented a language selector in the header component.
• Verified that all strings translate correctly for Spanish.

Testing Instructions

Checklist

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  PRs) or the media properties generator (ov just catalog/generate-docs media-props
  for the catalog or ov just api/generate-docs for the API) where applicable.

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[dhruvkb]

@yashhhYB is this fixing an open issue on Openverse? If not a rationale for the PR would be helpful.

Also I've restored the PR template in your PR description. Please populate the placeholders in the template, instead of replacing it with a freeform description.