add empty flutter web package

packages/z-timeline/lib/main.dart

@@ -0,0 +1,16 @@
+import 'package:flutter/material.dart';
+
+void main() {
+  runApp(const MainApp());
+}
+
+class MainApp extends StatelessWidget {
+  const MainApp({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    return const MaterialApp(
+      home: Scaffold(body: Center(child: Text('Hello World!'))),
+    );
+  }
+}