Examine source code of Robots.txt Checker

{
  "manifest_version": 2,
  "name": "Robots.txt Checker",
  "version": "1.0",
  "description": "Check Robots.txt on websites",
  "permissions": [
    "http://*/*",
    "https://*/*"
  ],
  "icons": {
    "48": "icon.jpg"
  },
  "browser_action": {
    "default_icon": "icon.jpg",
    "default_popup": "popup.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{0e8f5034-ed3b-4bc0-9022-58f7f342bb68}"
    }
  }
}