Examine source code of Duplicate Tab Detector

{
  "manifest_version": 3,
  "name": "Duplicate Tab Detector",
  "version": "2.5.3",
  "description": "Automatically detects and closes duplicate tabs in your current window or across all windows for a cleaner browsing experience.",
  "permissions": [
    "tabs",
    "storage",
    "windows"
  ],
  "background": {
    "page": "background.html"
  },
  "action": {
    "default_popup": "popup.html",
    "default_icon": {
      "16": "images/dd-16.png",
      "48": "images/dd-48.png",
      "128": "images/dd-128.png"
    }
  },
  "commands": {
    "_execute_action": {
      "suggested_key": {
        "default": "Ctrl+Shift+D",
        "mac": "Alt+D"
      }
    }
  },
  "icons": {
    "16": "images/dd-16.png",
    "48": "images/dd-48.png",
    "128": "images/dd-128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "duplicate-tab-detector@addons.mozilla.org"
    }
  }
}