Add README_CN.md

[ZMM-zhangmanman]

1. What kind of change does this PR introduce? (Bug fix, feature, docs update, …)
   This is a documentation update (i18n/translation). It introduces a new localized file (README_CN.md) and does not modify any existing code, configuration, or the original README.md.

2. Why was this change needed? (You can also link to an open issue here)
   This change is needed to make DocsGPT accessible and welcoming to the vast Chinese-speaking developer community, which is a major and active segment of the global open-source audience. An official, accurate translation:

Lowers the entry barrier by providing clear setup and usage instructions in the user‘s native language.

Reduces misunderstanding caused by unreliable browser translation of technical terms.

Demonstrates international support and encourages broader adoption and contributions.

Link to Issue: #[2208]

3. Other information:
   File: README_CN.md (new, in repository root).

Fidelity: All links, images, code blocks, and project structure are preserved identically. Technical terms are kept in English for accuracy.

Quality: This is a human-translated, proofread version aimed at natural fluency for native readers.

Maintenance: The original README.md remains the default and is completely unaffected.

[vercel]

@ZMM-zhangmanman is attempting to deploy a commit to the Arc53 Team on Vercel.

A member of the Team first needs to authorize it.

[ZMM-zhangmanman]

Hi @dartpain / maintainers,

My recent PR [#2209] has triggered deployment previews on Vercel for nextra-docsgpt and oss-docsgpt. Since I‘m not a member of the Arc53 Team on Vercel, the deployments are currently blocked and require authorization from a team owner.

Could someone please review and approve the pending deployment requests in the Vercel dashboard when you have a moment? This would allow the previews to build so we can verify the changes visually.

Thank you!