docs: add experimental notice to STARTS WITH filter

[DerTimonius]

Pull Request

Related issue

Fixes #<issue_number> (no related issue)

What does this PR do?

• the STARTS WITH filter is an experimental feature
• the docs are currently not marking it as experimental
• this PR marks it as experimental and mentions that enabling the CONTAINS filter will also enable STARTS WITH and vice versa

when looking at the commit history it appears that it was marked as experimental before, but was removed at some point (I think during the migration to Mintlify?)

PR checklist

Please check if your PR fulfills the following requirements:

• Does this PR fix an existing issue, or have you listed the changes applied in the PR description (and why they are needed)?
• Have you read the contributing guidelines?
• Have you made sure that the title is accurate and descriptive of the changes?

Thank you so much for contributing to Meilisearch!

[guimachiavelli]

Thank you for your PR, @DerTimonius!

We have recently stabilised STARTS WITH, so it is no longer an experimental feature in the latest Meilisearch version.

Are you experiencing any issues with this filter operator?

Closing the PR, but feel free to respond—I'm happy to collect usage feedback and if necessary direct you to someone in our support staff.

[DerTimonius]

Ah okay, I pulled my local docker image about a month ago, probably just a day or two before the release of the stable filter 😅

Sorry for the noise then 😬

But I was wondering: what do you think about mentioning in the docs from which version an experimental feature has been stable? Or introduced with v1.18.0?