Update docs for regex matching for HTTPRoutes and GRPCRoutes

[salonichf5]

Proposed changes

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following format:

Problem: Users need updated documentation for regex matching header and query params for HTTPRoutes and GRPCRoutes

Solution: Adds documentation for advanced routing and gateway compatibility document.

Testing: Deploy preview

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If this PR addresses an issue on GitHub, ensure that you link to it here:

NGF Repository Story - nginx/nginx-gateway-fabric#1965

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[github-actions]

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[sjberman]

This should not be targeting main, this should target ngf-release-2.0. Main is for docs we want to be published right now.

[salonichf5]

I have hereby read the F5 CLA and agree to its terms