Examine source code of Dark Mode for HackerNews

{
  "description": "Dark mode for HackerNews",
  "manifest_version": 2,
  "name": "Dark mode for HackerNews",
  "version": "2.2",
  "homepage_url": "https://github.com/tpkahlon/dark-mode-hackernews",
  "icons": {
    "512": "icons/border-512.png"
  },
  "content_scripts": [
    {
      "matches": [
        "https://*/*"
      ],
      "js": [
        "index.js"
      ]
    }
  ],
  "background": {
    "scripts": [
      "index.js"
    ]
  }
}