Examine source code of Wikipedia Dark Mode

{
  "manifest_version": 2,
  "name": "Wikipedia Dark Theme",
  "version": "1.0",
  "description": "Dark theme for Wikipedia",
  "icons": {
    "32": "wikipedia-icon.png"
  },
  "content_scripts": [
    {
      "matches": [
        "https://*.wikipedia.org/*"
      ],
      "css": [
        "theme.css"
      ]
    }
  ]
}