Examine source code of Twitter Link Expander

{
  "manifest_version": 2,
  "name": "Twitter Link Expander",
  "version": "2.0",
  "description": "Replaces all shortened t.co links with actual links so that users can click links on Twitter pages without being tracked and allows an alternative to opt out of link shortening. Please note currently it only works on twitter.com pages.",
  "icons": {
    "32": "icon-32.png"
  },
  "applications": {
    "gecko": {
      "id": "jid1-DwRap1pOaj8qgQ@jetpack"
    }
  },
  "content_scripts": [
    {
      "js": [
        "jquery.js",
        "jquery.whenlive.js",
        "application.js"
      ],
      "matches": [
        "https://twitter.com/*"
      ],
      "run_at": "document_end"
    }
  ]
}