Update README.md

Author: gkorland

README.md

@@ -2,6 +2,7 @@
 [![CircleCI](https://circleci.com/gh/RedisGraph/redisgraph.js/tree/master.svg?style=svg)](https://circleci.com/gh/RedisGraph/redisgraph.js/tree/master)
 [![npm version](https://badge.fury.io/js/redisgraph.js.svg)](https://badge.fury.io/js/redisgraph.js)
 [![GitHub issues](https://img.shields.io/github/release/RedisGraph/redisgraph.js.svg)](https://github.com/RedisGraph/redisgraph.js/releases/latest)
+[![Codecov](https://codecov.io/gh/RedisGraph/redisgraph.js/branch/master/graph/badge.svg)](https://codecov.io/gh/RedisGraph/redisgraph.js)
 
 # redisgraph.js