doc(readme): add apache license v2 link.

doc(readme): add apache license v2 link.
diff --git a/README.md b/README.md
index 15d2c2f..d06ee59 100644
--- a/README.md
+++ b/README.md
@@ -1,5 +1,6 @@
 # rocketmq-client-python
 
+[![License](https://img.shields.io/badge/license-Apache%202-4EB1BA.svg)](https://www.apache.org/licenses/LICENSE-2.0.html)
 [![Build Status](https://travis-ci.org/apache/rocketmq-client-python.svg?branch=master)](https://travis-ci.org/apache/rocketmq-client-python)
 [![codecov](https://codecov.io/gh/apache/rocketmq-client-python/branch/ctypes/graph/badge.svg)](https://codecov.io/gh/apache/rocketmq-client-python/branch/ctypes)
 [![PyPI](https://img.shields.io/pypi/v/rocketmq-client-python.svg)](https://pypi.org/project/rocketmq-client-python)