Examine source code of Github Helper

{
  "author": "Varun Sridharan",
  "developer": {
    "name": "Varun Sridharan",
    "url": "https://codecanyon.net/user/varunsridharan/portfolio"
  },
  "homepage_url": "https://github.com/varunsridharan/firefox-github-helper",
  "applications": {
    "gecko": {
      "id": "githubhelper@varunsridharan23",
      "strict_min_version": "42.0"
    }
  },
  "manifest_version": 2,
  "name": "Github Helper",
  "version": "2.2resigned1",
  "description": "This addon add usefull buttons in repo listing @ github",
  "icons": {
    "48": "icon-48.jpg",
    "96": "icon-96.jpg"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.github.com/*"
      ],
      "js": [
        "src/size.js",
        "src/helper.js"
      ]
    }
  ],
  "permissions": [
    "*://api.github.com/repos/*",
    "storage"
  ]
}