error: The named parameter 'javascriptChannels' isn't defined.

I tried to include `javascriptChannels` as per example but it's not defined.
I checked in`lib/src`directory; it contains only two file that are `base.dart` and `webview_scaffold.dart`.
Also there is no parameter with name `javascriptChannels`.

Start by comparing the example that uses `javascriptChannels` with the plugin API in `lib/src/base.dart` and `lib/src/webview_scaffold.dart`. Confirm whether the example and implementation refer to different versions, then update the affected example or add the missing parameter as appropriate. Done means the documented example matches the available API and the parameter is recognized.

Written by the indexing model from the issue text.