Sheet constructor
      const
      Sheet({ 
    
- Key? key,
 - required Widget builder(
- BuildContext context
 
 - bool dismissible = true,
 
Creates a new Sheet with the required content builder and optional dismissibility.
Use within ArcaneApp to ensure theme adaptation; pair with DraggableScrollableSheet
for resizable sheets or KeyboardAvoider for form inputs.
Implementation
const Sheet({super.key, required this.builder, this.dismissible = true});