Add plural formatting, translate and tweak some accessibility strings in composer (#7997)
* add plural formatting and translate accessibility strings
* tweak accessibility label and add comments for translators
* fix
* tweak comments
* make label conditionally plural
* rm stray bracket
* try to fix prettier
* nope
* lint
* more lint
* prettier
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Co-authored-by: Hailey <me@haileyok.com>
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