add codecov badge

Author: niveditn

README.md

@@ -4,6 +4,7 @@
 
 [![Node CI](https://github.com/imagekit-developer/imagekit-react/workflows/Node%20CI/badge.svg)](https://github.com/imagekit-developer/imagekit-react/)
 [![npm version](https://img.shields.io/npm/v/imagekitio-react)](https://www.npmjs.com/package/imagekitio-react)
+[![codecov](https://codecov.io/gh/imagekit-developer/imagekit-react/branch/master/graph/badge.svg)](https://codecov.io/gh/imagekit-developer/imagekit-react)
 [![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](https://opensource.org/licenses/MIT)
 [![Twitter Follow](https://img.shields.io/twitter/follow/imagekitio?label=Follow&style=social)](https://twitter.com/ImagekitIo)