added example

Author: hoc081098

README.md

@@ -5,3 +5,35 @@
 
 [![Pub Version](https://img.shields.io/pub/v/listenable_stream?style=plastic)](https://pub.dev/packages/listenable_stream)
 [![codecov](https://codecov.io/gh/Flutter-Dart-Open-Source/listenable_stream/branch/master/graph/badge.svg?token=6eORcR6Web)](https://codecov.io/gh/Flutter-Dart-Open-Source/listenable_stream)
+
+## Listenable.toStream()
+```dart
+final ChangeNotifier changeNotifier = ChangeNotifier();
+final Stream<ChangeNotifier> stream = changeNotifier.toStream();
+stream.listen(print); // prints Instance of 'ChangeNotifier', Instance of 'ChangeNotifier'
+
+changeNotifier.notifyListeners();
+changeNotifier.notifyListeners();
+```
+
+## ValueListenable.toValueStream()
+```dart
+final ValueNotifier<int> valueNotifier = ValueNotifier(0);
+final ValueStream<int> stream = valueNotifier.toValueStream();
+stream.listen(print); // prints 1, 2
+
+valueNotifier.value = 1;
+valueNotifier.value = 2;
+print(stream.value); // prints 2
+```
+
+## ValueListenable.toValueStream(replay: true)
+```dart
+final ValueNotifier<int> valueNotifier = ValueNotifier(0);
+final ValueStream<int> stream = valueNotifier.toValueStream(replay: true);
+stream.listen(print); // prints 0, 1, 2
+
+valueNotifier.value = 1;
+valueNotifier.value = 2;
+print(stream.value); // prints 2
+```