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/community/code-of-conduct.md

@@ -0,0 +1,44 @@
+---
+title: Kubernetes 社区行为规范
+layout: basic
+cid: community
+community_styles_migrated: true
+---
+
+<!-- ---
+title: Kubernetes Community Code of Conduct
+layout: basic
+cid: community
+community_styles_migrated: true
+--- -->
+
+<div class="community-section" id="cncf-code-of-conduct-intro">
+<p>
+<!-- Kubernetes follows the
+<a href="https://github.com/cncf/foundation/blob/master/code-of-conduct.md">CNCF Code of Conduct</a>.
+The text of the CNCF CoC is replicated below, as of
+<a href="https://github.com/cncf/foundation/blob/0ce4694e5103c0c24ca90c189da81e5408a46632/code-of-conduct.md">commit 0ce4694</a>.
+If you notice that this is out of date, please
+<a href="https://github.com/kubernetes/website/issues/new">file an issue</a>. -->
+Kubernetes 遵循
+<a href="https://github.com/cncf/foundation/blob/master/code-of-conduct-languages/zh.md">CNCF 行为规范</a>。
+CNCF 社区规范文本如下链接
+<a href="https://github.com/cncf/foundation/blob/0ce4694e5103c0c24ca90c189da81e5408a46632/code-of-conduct.md">commit 0ce4694</a>。
+如果你发现这个 CNCF 社区规范文本已经过时，请
+<a href="https://github.com/kubernetes/website/issues/new">提交 issue</a>。
+</p>
+
+<p>
+<!-- If you notice a violation of the Code of Conduct at an event or meeting, in
+Slack, or in another communication mechanism, reach out to
+the [Kubernetes Code of Conduct Committee](https://github.com/kubernetes/community/tree/master/committee-code-of-conduct) <conduct@kubernetes.io>.
+Your anonymity will be protected. -->
+
+如果你在活动、会议、Slack 或是其它场合发现有任何违反行为规范的行为，请联系[Kubernetes 行为规范委员会](https://github.com/kubernetes/community/tree/master/committee-code-of-conduct)<conduct@kubernetes.io>。
+我们会确保你的匿名性。
+</p>
+</div>
+
+<div id="cncf_coc_container">
+{{< include "/static/cncf-code-of-conduct.md" >}}
+</div>