Examine source code of Quick Highlights

{
  "manifest_version": 3,
  "name": "Quick Highlights",
  "version": "2.7.6",
  "description": "Simple, shortcut-based text highlighter with four colours.",
  "browser_specific_settings": {
    "gecko": {
      "id": "quick-highlights@extension",
      "strict_min_version": "142.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "icons": {
    "16": "icon16.png",
    "48": "icon48.png",
    "128": "icon128.png"
  },
  "permissions": [
    "clipboardWrite"
  ],
  "action": {
    "default_icon": {
      "16": "icon16.png",
      "48": "icon48.png",
      "128": "icon128.png"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "run_at": "document_start",
      "all_frames": true,
      "js": [
        "content.js"
      ],
      "css": [
        "styles.css"
      ]
    }
  ]
}