Examine source code of Rick Roll Detector

{
  "manifest_version": 2,
  "name": "Rick Roll Detector",
  "version": "1.0",
  "description": "Tiny extension to warn you if a page is trying to Rick Roll you.",
  "icons": {
    "48": "assets/icon_48x48.jpg"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "detect.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{6ed15339-de3a-4521-a068-b4f85d82fd71}"
    }
  }
}