Add traffic splitting example

Author: Kate Osborn

examples/traffic-splitting/README.md

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+# Example
+
+In this example we will deploy NGINX Kubernetes Gateway and configure traffic splitting for a simple cafe application.
+We will use `HTTPRoute` resources to split traffic between two versions of the application -- `coffee-v1` and `coffee-v2`.
+
+## Running the Example
+
+## 1. Deploy NGINX Kubernetes Gateway
+
+1. Follow the [installation instructions](/docs/installation.md) to deploy NGINX Gateway.
+
+1. Save the public IP address of NGINX Kubernetes Gateway into a shell variable:
+
+   ```
+   GW_IP=XXX.YYY.ZZZ.III
+   ```
+
+1. Save the port of NGINX Kubernetes Gateway:
+
+   ```
+   GW_PORT=<port number>
+   ```
+
+## 2. Deploy the Coffee Application
+
+1. Create the Cafe Deployments and Services:
+
+   ```
+   kubectl apply -f cafe.yaml
+   ```
+
+1. Check that the Pods are running in the `default` namespace:
+
+   ```
+   kubectl -n default get pods
+   NAME                         READY   STATUS    RESTARTS   AGE
+   coffee-v1-7c57c576b-rfjsh    1/1     Running   0          21m
+   coffee-v2-698f66dc46-vcb6r   1/1     Running   0          21m
+   ```
+
+## 3. Configure Routing
+
+1. Create the `Gateway`:
+
+   ```
+   kubectl apply -f gateway.yaml
+   ```
+
+1. Create the `HTTPRoute` resources:
+
+   ```
+   kubectl apply -f cafe-route.yaml
+   ```
+   
+This `HTTPRoute` resource defines a route for the path `/coffee` that sends 80% of the requests to `coffee-v1` and 20% to `coffee-v2`.
+
+## 4. Test the Application
+
+To access the application, we will use `curl` to send requests to `/coffee`:
+
+```
+curl --resolve cafe.example.com:$GW_PORT:$GW_IP http://cafe.example.com:$GW_PORT/coffee
+```
+
+80% of the responses will come from `coffee-v1`:
+
+```
+Server address: 10.12.0.18:80
+Server name: coffee-v1-7c57c576b-rfjsh
+```
+
+20% of the responses will come from `coffee-v2`:
+
+```
+Server address: 10.12.0.19:80
+Server name: coffee-v2-698f66dc46-vcb6r
+```

examples/traffic-splitting/cafe-route.yaml

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+apiVersion: gateway.networking.k8s.io/v1beta1
+kind: HTTPRoute
+metadata:
+  name: cafe-route
+spec:
+  parentRefs:
+  - name: gateway
+    sectionName: http
+  hostnames:
+  - "cafe.example.com"
+  rules:
+  - matches:
+    - path:
+        type: PathPrefix
+        value: /coffee
+    backendRefs:
+    - name: coffee-v1
+      port: 80
+      weight: 80
+    - name: coffee-v2
+      port: 80
+      weight: 20

examples/traffic-splitting/cafe.yaml

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+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: coffee-v1
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      app: coffee-v1
+  template:
+    metadata:
+      labels:
+        app: coffee-v1
+    spec:
+      containers:
+      - name: coffee-v1
+        image: nginxdemos/nginx-hello:plain-text
+        ports:
+        - containerPort: 8080
+---
+apiVersion: v1
+kind: Service
+metadata:
+  name: coffee-v1
+spec:
+  ports:
+  - port: 80
+    targetPort: 8080
+    protocol: TCP
+    name: http
+  selector:
+    app: coffee-v1
+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: coffee-v2
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      app: coffee-v2
+  template:
+    metadata:
+      labels:
+        app: coffee-v2
+    spec:
+      containers:
+      - name: coffee-v2
+        image: nginxdemos/nginx-hello:plain-text
+        ports:
+        - containerPort: 8080
+---
+apiVersion: v1
+kind: Service
+metadata:
+  name: coffee-v2
+spec:
+  ports:
+  - port: 80
+    targetPort: 8080
+    protocol: TCP
+    name: http
+  selector:
+    app: coffee-v2

examples/traffic-splitting/gateway.yaml

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+apiVersion: gateway.networking.k8s.io/v1beta1
+kind: Gateway
+metadata:
+  name: gateway
+  labels:
+    domain: k8s-gateway.nginx.org
+spec:
+  gatewayClassName: nginx
+  listeners:
+  - name: http
+    port: 80
+    protocol: HTTP