Examine source code of MDN_DarkMode

{
  "manifest_version": 2,
  "name": "MDN_DM",
  "description": "Dark Mode for MDN",
  "version": "0.0.2",
  "icons": {
    "64": "icons/icon.png"
  },
  "content_scripts": [
    {
      "matches": [
        "https://developer.mozilla.org/*"
      ],
      "css": [
        "style.css"
      ]
    }
  ]
}