Examine source code of Web Dark Mode Plus

{
  "name": "WhatsApp Web Dark Mode",
  "version": "1.0",
  "description": "The extension helps change the look and feel of WhatsApp Web to a dark theme by adding a 'dark' layer to the content element, providing a more comfortable browsing experience, especially in low-light environments",
  "manifest_version": 2,
  "permissions": [
    "activeTab"
  ],
  "content_scripts": [
    {
      "matches": [
        "https://web.whatsapp.com/*"
      ],
      "js": [
        "darkify.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{95db7798-188b-4554-ab68-b34286818c28}"
    }
  }
}