add travis badge

Author: 2hmad

README.md

@@ -8,6 +8,7 @@
 [![GitHub license](https://img.shields.io/github/license/gopulse/pulse)](LICENSE)
 [![Go Reference](https://pkg.go.dev/badge/github.com/gopulse/pulse.svg)](https://pkg.go.dev/github.com/gopulse/pulse)
 [![Go Doc](https://img.shields.io/badge/%F0%9F%93%9A%20godoc-pkg-00ACD7.svg?color=00ACD7&style=flat-square)](https://pkg.go.dev/github.com/gopulse/pulse#pkg-overview)
+[![Build Status](https://travis-ci.com/gopulse/pulse.svg?branch={branch})](https://travis-ci.com/gopulse/pulse)
 
 </div>