Add Flutter GUI example for VAD with a microphone. (#905)

sherpa-onnx/flutter/example/lib/utils.dart

@@ -2,6 +2,7 @@
 import 'package:path/path.dart';
 import 'package:path_provider/path_provider.dart';
 import 'package:flutter/services.dart' show rootBundle;
+import 'dart:typed_data';
 import "dart:io";
 
 // Copy the asset file from src to dst
@@ -16,3 +17,16 @@ Future<String> copyAssetFile({required String src, required String dst}) async {
 
   return target;
 }
+
+Float32List convertBytesToFloat32(Uint8List bytes, [endian = Endian.little]) {
+  final values = Float32List(bytes.length ~/ 2);
+
+  final data = ByteData.view(bytes.buffer);
+
+  for (var i = 0; i < bytes.length; i += 2) {
+    int short = data.getInt16(i, endian);
+    values[i ~/ 2] = short / 32678.0;
+  }
+
+  return values;
+}