Examine source code of Night Mode Toggle is

{
  "manifest_version": 2,
  "name": "Night Mode Toggle",
  "version": "1.0",
  "description": "Toggle dark mode on any website with one click",
  "permissions": [
    "activeTab"
  ],
  "browser_action": {
    "default_icon": {
      "16": "icon.png"
    },
    "default_title": "Toggle Night Mode"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{cb9de842-8002-49f4-9ab8-f4b50f180692}"
    }
  }
}