Examine source code of Responsive Check

{
  "manifest_version": 2,
  "name": "Responsive Test",
  "version": "1.0",
  "description": "Test website responsiveness",
  "permissions": [
    "tabs",
    "<all_urls>"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_title": "Test Responsiveness"
  },
  "web_accessible_resources": [
    "responsive.html",
    "load.js"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{298f725a-cc8d-465c-9607-ad18af430f8b}"
    }
  }
}