Examine source code of Form Guardian

{
  "manifest_version": 2,
  "name": "Form Guardian",
  "version": "1.1",
  "description": "Warns you when leaving a page with unsaved form data.",
  "author": "Uhuriicane",
  "icons": {
    "64": "icons/icon64.png",
    "128": "icons/icon128.png"
  },
  "browser_action": {
    "default_title": "Form Guardian",
    "default_popup": "popup.html",
    "default_icon": "icons/icon64.png"
  },
  "permissions": [
    "tabs",
    "activeTab"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_end"
    }
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{3ffd37e7-0f6a-4f85-bea3-a0650f59c356}",
      "strict_min_version": "58.0"
    }
  }
}