Examine source code of Favicon Detector Pro

{
  "manifest_version": 2,
  "name": "Favicon Detector",
  "author": "BlackGlory",
  "version": "4.1.2",
  "default_locale": "en",
  "description": "Click the extension button to detect current website's icons.",
  "icons": {
    "16": "assets/images/icon-16.png",
    "32": "assets/images/icon-32.png",
    "48": "assets/images/icon-48.png",
    "64": "assets/images/icon-64.png",
    "128": "assets/images/icon-128.png"
  },
  "browser_action": {
    "default_title": "Click the extension button to detect current website's icons.",
    "default_popup": "popup.html",
    "default_icon": {
      "16": "assets/images/icon-16.png",
      "32": "assets/images/icon-32.png",
      "48": "assets/images/icon-48.png",
      "64": "assets/images/icon-64.png",
      "128": "assets/images/icon-128.png"
    }
  },
  "permissions": [
    "activeTab",
    "scripting"
  ],
  "host_permissions": [
    "<all_urls>"
  ],
  "web_accessible_resources": [
    "assets/images/*"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{1772084c-7fc9-4b13-a05f-46f2fc9053d4}"
    }
  }
}