Examine source code of xkcd Companion

{
  "manifest_version": 2,
  "name": "xkcd-companion",
  "version": "0.0.3resigned1",
  "description": "A helpful addon for xkcd fans",
  "content_scripts": [
    {
      "matches": [
        "*://*.xkcd.com/*"
      ],
      "js": [
        "data/inject.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "@xkcd-companion"
    }
  }
}