Examine source code of Smart Night Mode

{
  "manifest_version": 3,
  "browser_specific_settings": {
    "gecko": {
      "id": "{a2764fc8-05ba-4808-919a-d5a28356c3d9}"
    }
  },
  "name": "Smart Dark Mode",
  "version": "2.0",
  "description": "Manipulate CSS to push dark mode in old websites.",
  "permissions": [
    "activeTab",
    "storage"
  ],
  "host_permissions": [
    "<all_urls>"
  ],
  "action": {
    "default_icon": {
      "16": "icons/icon16.png",
      "48": "icons/icon48.png",
      "128": "icons/icon128.png"
    },
    "default_title": "Dark Mode",
    "default_popup": "popup.html"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_idle"
    }
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "icons": {
    "16": "icons/icon16.png",
    "48": "icons/icon48.png",
    "128": "icons/icon128.png"
  }
}