feat: Chinese localization

### Describe Problem

The Chinese [community translation project in crowdin](https://crowdin.com/project/ionic-docs) is 100% complete.

But there is still no option to switch to Chinese in the [Documents page](https://ionicframework.com/docs).

### Describe Preferred Solution

The Chinese language option should appear in the language switching options in the [Documents page](https://ionicframework.com/docs).

### Describe Alternatives

_No response_

### Additional Information

_No response_

Start at the language-switching options on the Documents page and compare them with the completed Chinese translation in the Crowdin project. Locate the configuration or entry point that controls available locales; done means Chinese appears as a selectable option and links to the translated documentation.

由索引模型根据 Issue 内容生成。