Examine source code of SO Dark

{
  "manifest_version": 2,
  "name": "SO Dark",
  "version": "0.1.0",
  "description": "Set StackOverflow to respect the system theme without being logged in.",
  "permissions": [
    "http://*.stackoverflow.com/*",
    "https://*.stackoverflow.com/*",
    "http://stackoverflow.com/*",
    "https://stackoverflow.com/*"
  ],
  "content_scripts": [
    {
      "matches": [
        "http://*.stackoverflow.com/*",
        "https://*.stackoverflow.com/*",
        "http://stackoverflow.com/*",
        "https://stackoverflow.com/*"
      ],
      "js": [
        "set-theme.js"
      ]
    }
  ]
}