Add Patch Reader browser extension for Chrome and Edge

[Copilot]

• Set up project structure with npm/package.json
• Add diff2html dependency (local/offline)
• Create Chrome extension files:
  • manifest.json (v3)
  • background.js
  • diff-viewer.html (main page)
  • diff-viewer.js
  • styles.css
  • icons (16, 48, 128)
• Create Edge extension files (same structure)
• Add GitHub workflow files:
  • .github/dependabot.yml
  • .github/CODEOWNERS
  • .github/workflows/test.yml
  • .github/workflows/release.yml
  • .github/workflows/push-artifact.yml
• Build scripts for both browsers
• Test the extension functionality
• Take screenshots of the UI
• Run code review
• Run security scan (fixed workflow permissions)
• Refactor to eliminate duplicate code between Chrome and Edge

Refactoring

Moved shared files to src/common/ directory to eliminate code duplication:

• diff-viewer.html, diff-viewer.js, styles.css - shared UI files
• icons/ - shared icon files
• lib/ - shared diff2html library

Browser-specific files remain in src/chrome/ and src/edge/:

• manifest.json - browser-specific manifest
• background.js - browser-specific background script

Screenshots

UI After Refactoring

Original prompt

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This section details on the original issue you should resolve

<issue_title>功能需求</issue_title>
<issue_description>1. 提供谷歌浏览器和edge浏览器两个插件的构建
2. 提供.github下dependabot和codeowners 以及测试工作流，release发布时上传产物的工作流，每次推送到master分支时上传产物保留7天
3. 功能需求是，点击插件后，在浏览器创建一个html页面，在这个页面里可以上传patch/diff文件 或者手动输入文件内容，然后在另一个视图利用diff2html 渲染UI
4. 我希望默认左右布局，支持切换上下布局

5. 我希望不要用一些在线的css或者js或者api进行因为可能使用者处于无法连接外网的环境

Comments on the Issue (you are @copilot in this section)

• Fixes 功能需求 #1

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[unknowIfGuestInDream]

@copilot 谷歌浏览器和edge很多资源是一样的，是否存在重复代码的问题？

[Copilot]

@copilot 谷歌浏览器和edge很多资源是一样的，是否存在重复代码的问题？

已在 4d83567 中解决。将共享文件（diff-viewer.html、diff-viewer.js、styles.css、icons、lib）移至 src/common/ 目录，Chrome 和 Edge 只保留各自特有的文件（manifest.json、background.js）。构建脚本会在打包时将 common 目录的文件复制到两个浏览器的输出目录。

新的项目结构：

src/
├── common/           # 共享文件
│   ├── diff-viewer.html
│   ├── diff-viewer.js
│   ├── styles.css
│   ├── icons/
│   └── lib/
├── chrome/           # Chrome 特有文件
│   ├── manifest.json
│   └── background.js
└── edge/             # Edge 特有文件
    ├── manifest.json
    └── background.js