Update docs for new ingress api in cluster version >=1.19 (#7264)

* Update docs to support Ingress in cluster version 1.19 or greater

* Update docs

* Update basic-usage.md

* Update basic-usage.md

docs/user-guide/basic-usage.md

@@ -49,6 +49,54 @@ spec:
 When you apply this yaml, 2 ingress resources will be created managed by the **ingress-nginx** instance. Nginx is configured to automatically discover all ingress with the `kubernetes.io/ingress.class: "nginx"` annotation.
 Please note that the ingress resource should be placed inside the same namespace of the backend resource.
 
+If cluster version >= 1.19 the Ingress resource above will not work.
+You need to deploy the following so that it match the new api version.
+This will require changes to the Ingress objects as shown below, and a new object from type "kind: IngressClass"
+```
+apiVersion: networking.k8s.io/v1
+kind: Ingress
+metadata:
+  name: ingress-myservicea
+spec:
+  rules:
+  - host: myservicea.foo.org
+    http:
+      paths:
+      - path: /
+        pathType: Prefix
+        backend:
+          service:
+            name: myservicea
+            port: 
+              number: 80
+  ingressClassName: nginx
+---
+apiVersion: networking.k8s.io/v1
+kind: Ingress
+metadata:
+  name: ingress-myserviceb
+spec:
+  rules:
+  - host: myserviceb.foo.org
+    http:
+      paths:
+      - path: /
+        pathType: Prefix
+        backend:
+          service:
+            name: myserviceb
+            port: 
+              number: 80
+  ingressClassName: nginx
+---
+apiVersion: networking.k8s.io/v1
+kind: IngressClass
+metadata:
+  name: nginx
+spec:
+  controller: k8s.io/ingress-nginx
+```
+
 On many cloud providers ingress-nginx will also create the corresponding Load Balancer resource. All you have to do is get the external IP and add a DNS `A record` inside your DNS provider that point myServiceA.foo.org and myServiceB.foo.org to the nginx external IP. Get the external IP by running:
 
 ```