chore: adding the scrollToZoom option to test inside the themes example

Author: pavanpodila

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

@@ -16,6 +16,7 @@ class _ThemingExampleState extends State<ThemingExample> {
   late final NodeFlowController<Map<String, dynamic>> _controller;
   late NodeFlowTheme _theme;
   PortShape _selectedPortShape = PortShapes.capsuleHalf;
+  bool _scrollToZoom = true;
 
   @override
   void initState() {
@@ -242,6 +243,7 @@ class _ThemingExampleState extends State<ThemingExample> {
         controller: _controller,
         nodeBuilder: _buildNode,
         theme: _theme,
+        scrollToZoom: _scrollToZoom,
       ),
       children: [
         _buildThemePresets(),
@@ -258,6 +260,8 @@ class _ThemingExampleState extends State<ThemingExample> {
         const SizedBox(height: 24),
         _buildGridSection(),
         const SizedBox(height: 24),
+        _buildViewportSection(),
+        const SizedBox(height: 24),
         _buildNodeBorderSection(),
       ],
     );
@@ -756,6 +760,30 @@ class _ThemingExampleState extends State<ThemingExample> {
     );
   }
 
+  Widget _buildViewportSection() {
+    return Column(
+      crossAxisAlignment: CrossAxisAlignment.stretch,
+      children: [
+        const SectionTitle('Viewport'),
+        const SizedBox(height: 12),
+        Row(
+          children: [
+            const Text('Scroll to Zoom', style: TextStyle(fontSize: 12)),
+            const Spacer(),
+            Switch(
+              value: _scrollToZoom,
+              onChanged: (value) {
+                setState(() {
+                  _scrollToZoom = value;
+                });
+              },
+            ),
+          ],
+        ),
+      ],
+    );
+  }
+
   Widget _buildNodeBorderSection() {
     return Column(
       crossAxisAlignment: CrossAxisAlignment.stretch,