Examine source code of Notification Beat

{
  "manifest_version": 2,
  "name": "Notification Beat",
  "version": "1.0",
  "description": "Thay vì ping, phát một đoạn 'beat drop' khi trang web tạo Notification.",
  "permissions": [
    "<all_urls>"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_start"
    }
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": "icon.png",
    "default_title": "Notification Beat"
  },
  "icons": {
    "48": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{312fa9db-b2d8-49f3-8590-1eaabc2b5ae4}"
    }
  }
}