Add example for r2pipe-ffi

dart/r2pipe-ffi.dart

@@ -14,6 +14,29 @@ typedef RCoreNew = ffi.Pointer Function();
 typedef RCoreFreeFunc = ffi.Void Function(ffi.Pointer);
 typedef RCoreFree = void Function(ffi.Pointer);
 
+/*
+   https://pub.dev/packages/ffi/example
+   ------------------------------------
+
+import 'dart:ffi';
+import 'package:ffi/ffi.dart';
+
+void main() {
+  // Allocate and free some native memory with calloc and free.
+  final pointer = calloc<Uint8>();
+  pointer.value = 3;
+  print(pointer.value);
+  calloc.free(pointer);
+
+  // Use the Utf8 helper to encode zero-terminated UTF-8 strings in native memory.
+  final String myString = '😎👿💬';
+  final Pointer<Utf8> charPointer = myString.toNativeUtf8();
+  print('First byte is: ${charPointer.cast<Uint8>().value}');
+  print(charPointer.toDartString());
+  calloc.free(charPointer);
+}
+
+*/
 
 void main() {
    print('Hello Radare2 from Dart!');