feat: set default data values for viewport animation pipelines

Author: pavanpodila

packages/demo/lib/examples/advanced/viewport_animations.dart

@@ -140,7 +140,7 @@ class _ViewportAnimationsExampleState extends State<ViewportAnimationsExample> {
         position: const Offset(80, 80),
         size: const Size(700, 280),
         title: 'Main Pipeline',
-        data: '',
+        data: 'Main Pipeline',
         color: Colors.blue.withValues(alpha: 0.1),
         behavior: GroupBehavior.bounds,
         zIndex: -1,
@@ -153,7 +153,7 @@ class _ViewportAnimationsExampleState extends State<ViewportAnimationsExample> {
         position: const Offset(830, 80),
         size: const Size(300, 280),
         title: 'Outputs',
-        data: '',
+        data: 'Outputs',
         color: Colors.orange.withValues(alpha: 0.1),
         behavior: GroupBehavior.bounds,
         zIndex: -1,