New file:
* `html_page.dart`: Displays as widgets a HTML page
Impacted files:
* `attribute_card.dart`: added a barcode parameter that is needed (only) for ecoscore details; added a "details" button for ecoscore with html page display
* `attribute_list_expandable.dart`: added a now relevant barcode parameter to `AttributeCard`
* `pubspec.yaml`: added `flutter_widget_from_html_core` for html page display