Examine source code of Toggle Dark Mode

{
  "manifest_version": 2,
  "name": "Toggle Dark Mode",
  "version": "1.0",
  "description": "Quickly toggle dark mode on any webpage with one click.",
  "browser_action": {
    "default_icon": "icon.png",
    "default_title": "Toggle Dark Mode"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "permissions": [
    "activeTab"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{73069363-8cf1-4992-a052-7528214f7dc0}"
    }
  }
}