docs: Add Chinese translation

[Otto-J]

Why:

Some of the content here is not translated into Chinese.

What's being changed:

All content is translated into Chinese.

Check off the following:

• All of the tests are passing.
• I have reviewed my changes in staging.
• For content changes, I have reviewed the localization checklist
• For content changes, I have reviewed the Content style guide for GitHub Docs.

[janiceilene]

Thanks for opening this pull request @Otto-J! Unfortunately, we are not able to accept pull requests for translated content. Our translation process involves an integration with an external service at crowdin.com, where all translation activity happens. We hope to eventually open up the translation process to the open-source community, but we're not there yet.

See https://github.com/github/docs/blob/main/CONTRIBUTING.md#earth_asia-translations for more details.