Update README.md

Author: Ahmedatef5O5

README.md

@@ -1,6 +1,7 @@
 # Flutter samples
 
 [![Build Status](https://github.com/flutter/samples/workflows/Main%20Branch%20CI/badge.svg)](https://github.com/flutter/samples/actions?workflow=Main%20Branch%20CI)
+[![Flutter](https://img.shields.io/badge/flutter-3.13-blue)](https://flutter.dev)
 
 A collection of open source samples that illustrate best practices for
 [Flutter].