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/admin/konnectivity/egress-selector-configuration.yaml

@@ -0,0 +1,21 @@
+apiVersion: apiserver.k8s.io/v1beta1
+kind: EgressSelectorConfiguration
+egressSelections:
+# Since we want to control the egress traffic to the cluster, we use the
+# "cluster" as the name. Other supported values are "etcd", and "master".
+- name: cluster
+  connection:
+    # This controls the protocol between the API Server and the Konnectivity
+    # server. Supported values are "GRPC" and "HTTPConnect". There is no
+    # end user visible difference between the two modes. You need to set the
+    # Konnectivity server to work in the same mode.
+    proxyProtocol: GRPC
+    transport:
+      # This controls what transport the API Server uses to communicate with the
+      # Konnectivity server. UDS is recommended if the Konnectivity server
+      # locates on the same machine as the API Server. You need to configure the
+      # Konnectivity server to listen on the same UDS socket.
+      # The other supported transport is "tcp". You will need to set up TLS 
+      # config to secure the TCP transport.
+      uds:
+        udsName: /etc/kubernetes/konnectivity-server/konnectivity-server.socket