Update Kubernetes Documentation for new Gateway API features

[candita]

What would you like to be added:

https://kubernetes.io/docs/concepts/services-networking/gateway/ should be updated with new GA feaures.

Why this is needed:

https://kubernetes.io/docs/concepts/services-networking/ingress/ has already been listed as frozen in v1.19, with new features being added to the documentation link above. We have not significantly updated that link since GA.

[k8s-triage-robot]

The Kubernetes project currently lacks enough contributors to adequately respond to all issues.

This bot triages un-triaged issues according to the following rules:

• After 90d of inactivity, lifecycle/stale is applied
• After 30d of inactivity since lifecycle/stale was applied, lifecycle/rotten is applied
• After 30d of inactivity since lifecycle/rotten was applied, the issue is closed

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/lifecycle stale

[youngnick]

I'd forgotten about this, good bot for reminding us. Definitely not stale, we should probably consider making updating the upstream reference page part of our release process.

Thoughts @robscott @shaneutt @mlavacca ?

/remove-lifeycle stale

[shaneutt]

Documentation is a window into the project for the vast majority of people, so it seems reasonable to consider this a high priority to get done soon:

/priority important-soon

And we would appreciate any contributor who wants to help out with this:

/help