[adaptive_navigation] Enhance AdaptiveScaffold (#59)
[adaptive_navigation] Enhance AdaptiveScaffold (#59)

* Change AdaptiveScaffold to StatelessWidget

* Add const to AdaptiveScaffold

* Add key to AdaptiveScaffold
material-components/material-components-flutter-experimental,material-components/material-components-flutter-experimental,material-components/material-components-flutter-experimental,material-components/material-components-flutter-experimental,material-components/material-components-flutter-experimental,material-components/material-components-flutter-experimental