Examine source code of Page Change Watcher

{
  "manifest_version": 2,
  "name": "Page Change Watcher",
  "version": "1.0",
  "description": "Monitor a web page and notify you when its content changes.",
  "permissions": [
    "tabs",
    "activeTab",
    "notifications"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": true
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": {
      "48": "icon.png"
    }
  },
  "icons": {
    "48": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{83624d1f-db1e-4d77-9be5-575023b483c6}"
    }
  }
}