How to launch/load local html for iOS?

I have a html file in assets/index.html, I can launch it for Android use the url like:

```dart
String localUrl = 'file:///android_asset/flutter_assets/assets/index.html';
```

What url should I use for iOS? Following is the launch code:

```dart
_flutterWebviewPlugin.launch(
localUrl,
ignoreSSLErrors: true,
withLocalUrl: true,
localUrlScope: 'assets/',
allowFileURLs: true,
hidden: true
);
```

The issue identifies assets/index.html and the _flutterWebviewPlugin.launch call, but no implementation file or test. Start by reviewing the plugin's iOS local-file handling and existing usage examples. Done would be a documented, verified iOS loading pattern.

Written by the indexing model from the issue text.