Document how to do method matching in HTTPProxy

[m-yosefpor]

Please describe the problem you have

In #4088 there is an implementation for method matching in gateway API, but currently the HTTPProxy object does not support method matching, and it only supports routing based on path, headers, or query parameters. We need to have methodMatching in HTTPProxy object as well.

We need to document how to do method matching in HTTPProxy kind, with enovy pseudo-headers via header matching :method.

[github-actions]

Hey @m-yosefpor! Thanks for opening your first issue. We appreciate your contribution and welcome you to our community! We are glad to have you here and to have your input on Contour. You can also join us on our mailing list and in our channel in the Kubernetes Slack Workspace

[m-yosefpor]

Ok I found this issue comment which has used pseudo-headers with a header matching: #2679 (comment)

So I'm changing this issue title to add the documentations for it.

[abhayporwals]

Hey @skriss !
As, I explored the codebase and Issue. We have to make a httpproxy-method-matching.md under design\ with appropriate resources. Am I right?

[skriss]

@professorabhay we can document this in the existing page covering route conditions (https://projectcontour.io/docs/main/config/request-routing/#conditions) -- source for that is https://github.com/projectcontour/contour/blob/main/site/content/docs/main/config/request-routing.md#conditions