Update documentation once v1.0 is released

[robscott]

This issue will contain a list of all changes we need to make once v1.0 has been released:

• Replace "upcoming v1.0 release" per Phasing out Beta from Versioning Guide #2446 (comment).
• Update Gateway, GatewayClass, and HTTPRoute examples to use "v1" instead of "v1beta1" (most are in examples directory, but some incomplete examples are embedded directly in site-src markdown)
• Update getting started guide to use v1.0 instead of v0.8.1 (https://gateway-api.sigs.k8s.io/guides/)
• Update readme to use v1.0 instead of v0.8.1

[sftim]

Would also be nice to make https://gateway-api.sigs.k8s.io/ visually match https://k8s.io/docs/ more closely.

Want changes to https://k8s.io/docs/ to make that easier? It's OK to ask.

[robscott]

Would also be nice to make https://gateway-api.sigs.k8s.io/ visually match https://k8s.io/docs/ more closely.

That would be great! Any tips for how we can do that?

[robscott]

Created #2718 to cover last remaining open item here. Closing this one out.