Examine source code of Change Form Notifier

{
  "manifest_version": 2,
  "name": "Change Form Notifier",
  "version": "1.0",
  "description": "Warns you before leaving the page if form content has been modified.",
  "icons": {
    "64": "icons/icon64.png",
    "128": "icons/icon128.png"
  },
  "permissions": [
    "<all_urls>"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{8921cc8a-8166-478a-a17e-1b309139d872}",
      "strict_min_version": "113.0"
    }
  }
}