[TASK] Try to read HTTP_ACCEPT_LANGUAGE, if present. Allow for ISO. A…

[ramonfincken]

Trac ticket: https://core.trac.wordpress.org/ticket/30049

[github-actions]

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Props swissspidy.

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[github-actions]

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[swissspidy]

There is already great progress over at #6623 with more edge cases covered and proper tests. I suggest focusing on that PR instead.