Add version button on the docs

[jesayafn]

What would you like to be added: Version button to choose desired version.

Why this is needed: For easier troubleshooting issues when using an earlier version.

Example:

$ kubectl apply -f all-in-one.yaml --dry-run=server
error: error validating "all-in-one.yaml": error validating data: [ValidationError(HTTPRoute.spec): unknown field "hostname" in io.k8s.networking.gateway.v1.HTTPRoute.spec, ValidationError(HTTPRoute.spec.rules[0]): unknown field "name" in io.k8s.networking.gateway.v1.HTTPRoute.spec.rules]; if you choose to ignore these errors, turn validation off with --validate=false

In this case, I don't know the v1.4.0 has been released. I'm reading the newer version while I'm troubleshooting the earlier version (v1.3.0).