Examine source code of GitHub Enhancing

{
  "manifest_version": 2,
  "name": "GitHub Enhancing",
  "version": "0.0.2",
  "description": "The Enhanced GitHub Theme.",
  "content_scripts": [
    {
      "matches": [
        "https://github.com/*"
      ],
      "js": [
        "index.js"
      ],
      "run_at": "document_end"
    }
  ],
  "icons": {
    "16": "img/16.png",
    "48": "img/48.png",
    "128": "img/128.png"
  },
  "browser_action": {
    "default_icon": {
      "19": "img/16.png",
      "38": "img/48.png"
    },
    "default_title": "GitHub Enhancing"
  }
}