Examine source code of Dark Mode for Wikipedia

{
  "manifest_version": 2,
  "name": "Dark Mode for Wikipedia",
  "version": "4.5.7",
  "description": "Wikipedia Dark Theme",
  "icons": {
    "48": "dark_wiki_icon.png"
  },
  "content_scripts": [
    {
      "run_at": "document_start",
      "matches": [
        "*://*.wikipedia.org/*"
      ],
      "js": [
        "contentScript.js"
      ],
      "css": [
        "background.css"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{886bbdf2-5241-4b91-b547-c7e8276bdc27}"
    }
  }
}