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/docs/reference/glossary/container-runtime-interface.md

@@ -0,0 +1,42 @@
+---
+title: 容器运行时接口
+id: container-runtime-interface
+date: 2021-11-24
+full_link: /zh/docs/concepts/architecture/cri
+short_description: >
+  kubelet 和容器运行时之间通信的主要协议。
+
+aka:
+tags:
+  - cri
+---
+
+<!--
+title: Container Runtime Interface
+id: container-runtime-interface
+date: 2021-11-24
+full_link: /docs/concepts/architecture/cri
+short_description: >
+  The main protocol for the communication between the kubelet and Container Runtime.
+
+aka:
+tags:
+  - cri
+-->
+
+<!-- The main protocol for the communication between the kubelet and Container Runtime. -->
+kubelet 和容器运行时之间通信的主要协议。
+
+<!--more-->
+
+<!-- 
+The Kubernetes Container Runtime Interface (CRI) defines the main
+[gRPC](https://grpc.io) protocol for the communication between the
+[cluster components](/docs/concepts/overview/components/#node-components)
+{{< glossary_tooltip text="kubelet" term_id="kubelet" >}} and
+{{< glossary_tooltip text="container runtime" term_id="container-runtime" >}}.
+-->
+Kubernetes 容器运行时接口（CRI）定义了主要 [gRPC](https://grpc.io) 协议，
+用于[集群组件](/zh/docs/concepts/overview/components/#node-components)
+{{< glossary_tooltip text="kubelet" term_id="kubelet" >}} 和
+{{< glossary_tooltip text="容器运行时" term_id="container-runtime" >}}。