added initialization scope & handling initialization state in runtime example

lib/src/initialization/initialization_step_label.dart

@@ -0,0 +1,13 @@
+import 'package:equatable/equatable.dart';
+import 'package:meta/meta.dart';
+
+@immutable
+abstract class InitializableStepLabel<T> with EquatableMixin {
+  final T value;
+
+  const InitializableStepLabel(this.value);
+
+  @override
+  @mustCallSuper
+  List<Object?> get props => [value];
+}