Examine source code of Catnip

{
  "manifest_version": 2,
  "name": "Catnip",
  "version": "1.0",
  "description": "Catnip gives you a button that replaces all images on your active browser tab with images of cats. Inject catnip into your browser today!",
  "permissions": [
    "activeTab"
  ],
  "icons": {
    "48": "icons/cat-48.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "browser_style": true,
    "default_icon": {
      "48": "icons/cat-48.png"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{d91e2f9f-8201-438d-b8da-923a632739f4}"
    }
  }
}