docs: add note about JavaScript-based locale files not being supported

[junwen-k]

This PR adds a note to clarify that JavaScript-based locale files (.js and .ts) are not currently supported, with a reference to the relevant GitHub issue.

This helps users understand the current limitations of the plugin and provides a link to track the feature request.

Thank you. #32

[changeset-bot]

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Latest commit: 1252ded

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