add empty line

Author: js1010

README.md

@@ -3,6 +3,7 @@
 [![License](https://img.shields.io/badge/License-Apache%202.0-blue.svg)](https://opensource.org/licenses/Apache-2.0)
 
 [![Build Status](https://travis-ci.org/cusim.svg?branch=main)](https://travis-ci.org/js1010/cusim)
+
 [![contributions welcome](https://img.shields.io/badge/contributions-welcome-brightgreen.svg?style=flat)](https://github.com/dwyl/learn-travis/issues)
 
 ### Introduction