docs: Add Chinese (Simplified) README translation

[xinyang20]

Proposal

Add a Chinese (Simplified) README file (README_CN.md) to improve accessibility for Chinese-speaking developers.

Motivation

• opcode is a powerful GUI tool for Claude Code with significant interest from the Chinese developer community
• Currently, only an external translation is available on zdoc.app, but there is no official Chinese documentation
  in the repository
• Having the translation in the repository is more reliable and discoverable
• Follows best practices of major open-source projects like Vue.js, React, and Vite

Implementation Plan

1. Create README_CN.md file with high-quality Chinese translation
2. Add language switcher links at the top of both README files
3. Maintain the same structure and formatting as the English version
4. Reference the excellent translation available on zdoc.app

✅ Translation Quality Assurance

I will ensure:

• Accurate technical terminology translation
• Fluent and natural Chinese expression
• All links and formatting preserved
• Code examples kept in English (standard practice)
• Regular synchronization with English version updates

Maintenance Plan

• Synchronize updates when the English README has major changes
• Indicate in PRs when the Chinese version needs updating
• Willing to maintain the Chinese translation long-term

Additional Context

• The zdoc.app translation (https://zdoc.app/zh/getAsterisk/opcode) is excellent and can serve as a reference
• Using README_CN.md as the filename for consistency
• This would be the first official in-repo translation, potentially paving the way for other languages

Looking forward to feedback and suggestions!

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中文说明

提议

为项目添加简体中文 README 文件（README_CN.md），提高中文开发者的访问便利性。

动机

• opcode 是 Claude Code 的强大 GUI 工具，在中文开发者社区有很大需求
• 目前只有 zdoc.app 外部平台的翻译，仓库内没有官方中文文档
• 在仓库内提供翻译更可靠、更易发现

翻译质量承诺

• 准确的技术术语翻译
• 流畅自然的中文表达
• 保留所有格式和链接
• 与英文版保持同步更新

期待您的反馈！