Enhancement: Make footers translatable.

[juanfra]

Description

I am adding i18n functions for footers.

I'm still doubtful we should include Twenty Twenty-Five as a hardcoded string in some footers. I know this discussion happened before. I believe that now that we have the copyright block binding, that's a good candidate. Else, re-consider the site title.

Screenshots

N/A

Testing Instructions

1. Open the site editor
2. Try every footer
3. Check that the strings are correct.

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Co-authored-by: juanfra <juanfra@git.wordpress.org>
Co-authored-by: carolinan <poena@git.wordpress.org>

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