docs(querying): add _params to api routes

[nobkd]

🔗 Linked issue

❓ Type of change

• 📖 Documentation (updates to the documentation or readme)
• 🐞 Bug fix (a non-breaking change that fixes an issue)
• 👌 Enhancement (improving an existing functionality like performance)
• ✨ New feature (a non-breaking change that adds functionality)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

Added example for _params api route endpoint.

📝 Checklist

• I have linked an issue or discussion.
• I have updated the documentation accordingly.

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[nobkd]

Feel free to provide a better example.
I think it's necessary to provide documentation for the _params endpoint to show how to make complex requests with api routes, instead of just explaining how it's possible with the queryContent function.

[farnabaz]

Thanks for the PR @nobkd,
Before we documented advanced usages of _params we need to expose util to encode/decode these as query params. These utils are responsible for preparing regex for query params.

I'm merging this, and updating docs once we exposed utils.