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/limitrange.md

@@ -0,0 +1,51 @@
+---
+title: LimitRange
+id: limitrange
+date: 2019-04-15
+full_link:  /docs/concepts/policy/limit-range/
+short_description: >
+  提供约束来限制命名空间中每个容器或 Pod 的资源消耗。
+
+aka: 
+tags:
+- core-object
+- fundamental
+- architecture
+related:
+ - pod
+ - container
+
+---
+
+<!--
+---
+title: LimitRange
+id: limitrange
+date: 2019-04-15
+full_link:  /docs/concepts/policy/limit-range/
+short_description: >
+  Provides constraints to limit resource consumption per Containers or Pods in a namespace.
+
+aka: 
+tags:
+- core-object
+- fundamental
+- architecture
+related:
+ - pod
+ - container
+
+---
+-->
+
+<!--
+ Provides constraints to limit resource consumption per {{< glossary_tooltip text="Containers" term_id="container" >}} or {{< glossary_tooltip text="Pods" term_id="pod" >}} in a namespace.
+-->
+ 提供约束来限制命名空间中每个 {{< glossary_tooltip text="容器（Containers）" term_id="container" >}} 或 {{< glossary_tooltip text="Pod" term_id="pod" >}} 的资源消耗。
+
+<!--more--> 
+<!--
+LimitRange limits the quantity of objects that can be created  by type, 
+as well as the amount of compute resources that may be requested/consumed by individual {{< glossary_tooltip text="Containers" term_id="container" >}} or {{< glossary_tooltip text="Pods" term_id="pod" >}} in a namespace.
+-->
+LimitRange 按照类型来限制命名空间中对象能够创建的数量，以及单个 {{< glossary_tooltip text="容器（Containers）" term_id="container" >}} 或 {{< glossary_tooltip text="Pod" term_id="pod" >}} 可以请求/使用的计算资源量。