FeedBack: Restrict allowed languages!

Hey everyone,

In this issue, we want to check the UTF-8 for different language.

### Goal
You can request a language, or discuss UTF-8... (regex)

### What's "data-filter-lang"?
An argument to restrict the allowed languages.

Regards,
Max

The issue does not identify a file, test, or implementation entry point. Begin by reviewing the proposed data-filter-lang argument and the library's input-filtering entry points, then clarify which languages and UTF-8 rules are supported before defining tests and an acceptance criterion.

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