Examine source code of Short URL Expander

{
  "manifest_version": 2,
  "name": "Short URL Expander",
  "version": "0.3resigned1",
  "description": "Adds an Expand Shortened URLs item to the context menu. Links on the page that contain shortened URLs will be resolved and replaced with their final URL.",
  "developer": {
    "name": "James Mazikowski",
    "url": "http://www.mazikowski.net"
  },
  "permissions": [
    "activeTab",
    "contextMenus",
    "https://unshorten.me/",
    "webRequest"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{de374d6d-45df-4ee6-a535-68e24cf9bcf6}"
    }
  }
}