feat: 增加中文文档（Add Chinese documents）

### Describe Problem

Describe Problem
The Chinese [community translation project in crowdin](https://crowdin.com/project/ionic-docs) is 100% complete.
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But there is still no option to switch to Chinese in the [Documents page](https://ionicframework.com/docs).
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Describe Preferred Solution
The Chinese language option should appear in the language switching options in the [Documents page](https://ionicframework.com/docs).
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Describe Alternatives
No response

Additional Information
No response

### Describe Preferred Solution

_No response_

### Describe Alternatives

_No response_

### Additional Information

_No response_

Start by locating the Documents page's language-switching configuration and checking how its Crowdin translations are represented. Add Chinese to the available options, then verify that it appears in the language switcher and links to the completed Chinese documentation.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.