fix(theme-translation): add missing Polish (pl) theme translations

[mariuszkrzaczkowski]

Pre-flight checklist

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• If this is a new API or substantial change: the PR has an accompanying issue (closes #0000) and the maintainers have approved on my working plan.

Motivation

Complete pl-PL translation.

Test Plan

Test links

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Related issues/PRs

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[slorber]

thanks 👍