Examine source code of Domain Age Check

{
  "name": "Domain Age Checker",
  "version": "0.1",
  "description": "Domain age checker is a whois tool / extension developed by Cynexium (Umar) for checking any domain's age",
  "permissions": [
    "activeTab",
    "storage"
  ],
  "background": {
    "scripts": [
      "worker.js"
    ],
    "persistent": false
  },
  "browser_action": {
    "default_popup": "ext.html",
    "default_icon": {
      "16": "assets/icon-16x16.png",
      "32": "assets/icon-32x32.png",
      "48": "assets/icon-48x48.png",
      "144": "assets/icon-144x144.png",
      "192": "assets/icon-192x192.png"
    }
  },
  "icons": {
    "16": "assets/icon-16x16.png",
    "32": "assets/icon-32x32.png",
    "48": "assets/icon-48x48.png",
    "144": "assets/icon-144x144.png",
    "192": "assets/icon-192x192.png"
  },
  "manifest_version": 2,
  "content_security_policy": "script-src 'self'; object-src 'self'",
  "browser_specific_settings": {
    "gecko": {
      "id": "{eb319548-467a-4b19-a124-24f6c68dbb95}"
    }
  }
}