Using WebviewScaffold to load URLs doesn't work in iOS

## System info

Issue occurs on: iOS
Plugin version: 0.4.0
Flutter doctor output:

```
Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel stable, 3.16.2, on macOS 14.1.2 23B92 darwin-arm64, locale en-IN)
[✓] Android toolchain - develop for Android devices (Android SDK version 34.0.0)
[✓] Xcode - develop for iOS and macOS (Xcode 15.0.1)
[✓] Chrome - develop for the web
[✓] Android Studio (version 2023.1)
[✓] Connected device (2 available)
[✓] Network resources

• No issues found!
```

## Steps to Reproduce

1. I am using the WebViewScaffold to launch a URL. This approach works fine on Android and the page is loaded. However, on iOS, it gives a white blank screen.
2. Followed all the steps mentioned in the documentation and the key "NSAppTransportSecurity" is added to the Info.plist file as recommended in the documentation.
3. The iOS app launches the URL and works fine if we use an instance of the FlutterWebViewPlugin to call the "launch()" method instead of the WebViewScaffold implementation.
4. There are no errors logged on the console while running it.
5. Here is the code that renders the view inside a StatefulWidget

```
...
return SafeArea(
child: WebviewScaffold(
url: _url,
mediaPlaybackRequiresUserGesture: false,
useWideViewPort: true,
appCacheEnabled: true,
geolocationEnabled: true,
invalidUrlRegex:
r'^(https:\/\/api\.whatsapp\.com|https:\/\/apps\.apple\.com|https:\/\/play\.google\.com|tel:|mailto:|https:\/\/www\.facebook\.com|https:\/\/www\.youtube\.com|https:\/\/www\.instagram\.com)',
debuggingEnabled: true,
),
);
```

## Logs

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```

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```

Comienza reproduciendo el comportamiento de iOS mediante el punto de entrada WebviewScaffold, comparándolo con FlutterWebViewPlugin.launch() y revisando la configuración documentada de Info.plist NSAppTransportSecurity. El issue no indica ningún archivo fuente ni prueba, así que primero localiza la implementación de WebView de iOS y establece una URL y un caso de fallo reproducibles; se considera completado cuando la URL se renderiza mediante WebviewScaffold en iOS sin introducir regresiones en el comportamiento de Android.

Escrito por el modelo de indexación a partir del texto del issue.