Examine source code of Dark Mode Switcher

{
  "manifest_version": 2,
  "name": "Dark Mode Switcher",
  "version": "1.0",
  "description": "Enable or disable dark mode on any page with one click.",
  "permissions": [
    "activeTab"
  ],
  "browser_action": {
    "default_title": "Toggle Dark Mode"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{610cc06e-90c2-41ec-8e57-42c8b820e280}"
    }
  }
}