Examine source code of 12ft Redirect

{
  "manifest_version": 2,
  "name": "12ft Redirect",
  "version": "1.0",
  "description": "Redirects the current URL through 12ft.io",
  "permissions": [
    "activeTab"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "browser_action": {
    "default_icon": {
      "48": "icon-48.png",
      "128": "icon-128.png"
    }
  },
  "icons": {
    "48": "icon-48.png",
    "128": "icon-128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{1d6d1a8c-fa00-4e2b-b178-551cd53147e0}"
    }
  }
}