Examine source code of Githubify

{
  "version": "1.1a",
  "manifest_version": 2,
  "name": "Githubify",
  "description": "Adds an option to update Your contrib chart",
  "content_scripts": [
    {
      "matches": [
        "*://github.com/*"
      ],
      "js": [
        "./src/githubify.js"
      ]
    }
  ],
  "icons": {
    "48": "./icons/48.png"
  },
  "author": "Roman Kozin"
}