Update README.md (#1258)

Add Jenkins master badge.
Signed-off-by: Lutkin Wang <yamasite@qq.com>

README.md

@@ -9,6 +9,7 @@
 [![codecov](https://codecov.io/gh/milvus-io/milvus/branch/master/graph/badge.svg)](https://codecov.io/gh/milvus-io/milvus)
 [![All Contributors](https://img.shields.io/badge/all_contributors-7-orange.svg?style=flat-square)](#contributors-)
 [![CII Best Practices](https://bestpractices.coreinfrastructure.org/projects/3563/badge)](https://bestpractices.coreinfrastructure.org/projects/3563)
+[![Build Status](http://internal.zilliz.com:18080/jenkins/job/milvus-ci/job/master/badge/icon)](http://internal.zilliz.com:18080/jenkins/job/milvus-ci/job/master/)
 
 [中文版](README_CN.md) | [日本語版](README_JP.md)