Add the ingressclass resource in the ingress RBAC documentation

Author: jbdoumenjou

docs/content/routing/providers/kubernetes-ingress.md

@@ -32,8 +32,10 @@ which in turn will create the resulting routers, services, handlers, etc.
           - watch
       - apiGroups:
           - extensions
+          - networking.k8s.io
         resources:
           - ingresses
+          - ingressclasses
         verbs:
           - get
           - list