[Doc] [KubeRay] Add GKE ingress doc (ray-project#38935)

Adds a doc section for setting up Ingress on GKE. At the end of the doc, the user will be able to view the Ray dashboard UI via the Ingress.

---------

Signed-off-by: Archit Kulkarni <architkulkarni@users.noreply.github.com>
Co-authored-by: angelinalg <122562471+angelinalg@users.noreply.github.com>
Co-authored-by: Kai-Hsun Chen <kaihsun@apache.org>

doc/source/cluster/kubernetes/k8s-ecosystem/ingress.md

@@ -5,12 +5,13 @@
 Two examples show how to use ingress to access your Ray cluster:
 
   * [AWS Application Load Balancer (ALB) Ingress support on AWS EKS](kuberay-aws-alb)
+  * [GKE Ingress support](kuberay-gke-ingress)
   * [Manually setting up NGINX Ingress on Kind](kuberay-nginx)
 
 (kuberay-aws-alb)=
 ## AWS Application Load Balancer (ALB) Ingress support on AWS EKS
 
-### Prerequisite
+### Prerequisites
 * Create an EKS cluster. See [Getting started with Amazon EKS – AWS Management Console and AWS CLI](https://docs.aws.amazon.com/eks/latest/userguide/getting-started-console.html#eks-configure-kubectl).
 
 * Set up the [AWS Load Balancer controller](https://github.com/kubernetes-sigs/aws-load-balancer-controller), see [installation instructions](https://kubernetes-sigs.github.io/aws-load-balancer-controller/latest/deploy/installation/). Note that the repository maintains a webpage for each release. Confirm that you are using the latest installation instructions.
@@ -72,6 +73,70 @@ kubectl describe ingress ray-cluster-ingress
 kubectl delete ingress ray-cluster-ingress
 ```
 
+(kuberay-gke-ingress)=
+
+## GKE Ingress support
+
+### Prerequisites
+
+* Create a GKE cluster and ensure that you have the kubectl tool installed and authenticated to communicate with your GKE cluster.  See [this tutorial](kuberay-gke-gpu-cluster-setup) for an example of how to create a GKE cluster with GPUs.  (GPUs are not necessary for this section.)
+
+* It may be helpful to understand the concepts at <https://cloud.google.com/kubernetes-engine/docs/concepts/ingress>.
+
+### Instructions
+Save the following file as `ray-cluster-gclb-ingress.yaml`:
+
+```yaml
+apiVersion: networking.k8s.io/v1
+kind: Ingress
+metadata:
+  name: ray-cluster-ingress
+  annotations:
+    kubernetes.io/ingress.class: "gce"
+spec:
+  rules:
+    - http:
+        paths:
+          - path: /
+            pathType: Prefix
+            backend:
+              service:
+                name: raycluster-kuberay-head-svc # Update this line with your head service in Step 3 below.
+                port:
+                  number: 8265
+```
+
+Now run the following commands:
+
+```bash
+# Step 1: Install KubeRay operator and CRD
+helm repo add kuberay https://ray-project.github.io/kuberay-helm/
+helm install kuberay-operator kuberay/kuberay-operator --version 0.6.0
+
+# Step 2: Install a RayCluster
+helm install raycluster kuberay/ray-cluster --version 0.6.0
+
+# Step 3: Edit ray-cluster-gclb-ingress.yaml to replace the service name with the name of the head service from the RayCluster. (Output of `kubectl get svc`)
+
+# Step 4: Apply the Ingress configuration
+kubectl apply -f ray-cluster-gclb-ingress.yaml
+
+# Step 5: Check ingress created by Step 4.
+kubectl describe ingress ray-cluster-ingress
+
+# Step 6: After a few minutes, GKE allocates an external IP for the ingress. Check it using:
+kubectl get ingress ray-cluster-ingress
+
+# Example output:
+# NAME                  CLASS    HOSTS   ADDRESS         PORTS   AGE
+# ray-cluster-ingress   <none>   *       34.160.82.156   80      54m
+
+# Step 7: Check Ray Dashboard by visiting the allocated external IP in your browser. (In this example, it is 34.160.82.156)
+
+# Step 8: Delete the ingress.
+kubectl delete ingress ray-cluster-ingress
+```
+
 (kuberay-nginx)=
 ## Manually setting up NGINX Ingress on Kind