Added documentation for new language filter for projects

What does this MR do and why?

This MR adds the documentation about the new language filter for projects 🙂

The feature is in the process of rolling out, so once that is fully completed the feature flag will be enabled to everyone (as mentioned in the docs).

Related issue: #385465 (closed)

Screenshots or screen recordings

N.A.

How to set up and validate locally

N.A.

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