Switch language name 'zh' to 'zh-cn'

This is the first step to rename 'zh' to 'zh-cn'. There are several reasons why we rename the language name.

- The upstream docsy theme changed the language name, leading to many warnings during site build;
  The side-effect is that the i18n strings are no longer working.
- We believe renaming the language is the right thing to do, because this move can make room for other variants of Chinese language, such as 'zh-tw', 'zh-sg' etc.

There would be several follow-ups to this PR, such as fixing the intra-site links, adding redirects etc.

We will lock up changes to zh/zh-cn pages for the moment, until this one gets in.

This PR is based on commit cdad0a7342.

content/zh-cn/examples/service/access/Dockerfile

@@ -0,0 +1,4 @@
+FROM nginx:1.17.3
+
+RUN rm /etc/nginx/conf.d/default.conf
+COPY frontend-nginx.conf /etc/nginx/conf.d

content/zh-cn/examples/service/access/backend-deployment.yaml

@@ -0,0 +1,26 @@
+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: backend
+spec:
+  selector:
+    matchLabels:
+      app: hello
+      tier: backend
+      track: stable
+  replicas: 3
+  template:
+    metadata:
+      labels:
+        app: hello
+        tier: backend
+        track: stable
+    spec:
+      containers:
+        - name: hello
+          image: "gcr.io/google-samples/hello-go-gke:1.0"
+          ports:
+            - name: http
+              containerPort: 80
+...

content/zh-cn/examples/service/access/backend-service.yaml

@@ -0,0 +1,14 @@
+---
+apiVersion: v1
+kind: Service
+metadata:
+  name: hello
+spec:
+  selector:
+    app: hello
+    tier: backend
+  ports:
+  - protocol: TCP
+    port: 80
+    targetPort: http
+...

content/zh-cn/examples/service/access/frontend-deployment.yaml

@@ -0,0 +1,27 @@
+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: frontend
+spec:
+  selector:
+    matchLabels:
+      app: hello
+      tier: frontend
+      track: stable
+  replicas: 1
+  template:
+    metadata:
+      labels:
+        app: hello
+        tier: frontend
+        track: stable
+    spec:
+      containers:
+        - name: nginx
+          image: "gcr.io/google-samples/hello-frontend:1.0"
+          lifecycle:
+            preStop:
+              exec:
+                command: ["/usr/sbin/nginx","-s","quit"]
+...

content/zh-cn/examples/service/access/frontend-nginx.conf

@@ -0,0 +1,14 @@
+# The identifier Backend is internal to nginx, and used to name this specific upstream
+upstream Backend {
+    # hello is the internal DNS name used by the backend Service inside Kubernetes
+    server hello;
+}
+
+server {
+    listen 80;
+
+    location / {
+        # The following statement will proxy traffic to the upstream named Backend
+        proxy_pass http://Backend;
+    }
+}

content/zh-cn/examples/service/access/frontend-service.yaml

@@ -0,0 +1,15 @@
+---
+apiVersion: v1
+kind: Service
+metadata:
+  name: frontend
+spec:
+  selector:
+    app: hello
+    tier: frontend
+  ports:
+  - protocol: "TCP"
+    port: 80
+    targetPort: 80
+  type: LoadBalancer
+...

content/zh-cn/examples/service/access/hello-application.yaml

@@ -0,0 +1,20 @@
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: hello-world
+spec:
+  selector:
+    matchLabels:
+      run: load-balancer-example
+  replicas: 2
+  template:
+    metadata:
+      labels:
+        run: load-balancer-example
+    spec:
+      containers:
+        - name: hello-world
+          image: gcr.io/google-samples/node-hello:1.0
+          ports:
+            - containerPort: 8080
+              protocol: TCP