Examine source code of Popup Dark Mode Toggle

{
  "manifest_version": 3,
  "name": "Popup Dark Mode Toggle",
  "version": "1.0",
  "description": "A dark/light theme toggle button for the extension's popup itself, demonstrating a theme switcher.",
  "action": {
    "default_popup": "popup.html",
    "default_icon": "popup_dark_mode_toggle.png"
  },
  "icons": {
    "128": "popup_dark_mode_toggle.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "qfeliciaduvalljbeos22@hotmail.com"
    }
  }
}