Examine source code of BIG FOX

{
  "manifest_version": 2,
  "name": "Invisible Finder",
  "version": "1.7",
  "description": "Highlights 'invisible', shows image, plays sound once per page load.",
  "permissions": [
    "<all_urls>"
  ],
  "web_accessible_resources": [
    "big.png",
    "invisible.mp3"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_idle"
    }
  ],
  "browser_action": {
    "default_title": "Invisible Finder"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{61b1472b-949b-439c-822c-794d3c9cb628}"
    }
  }
}