updated readme

Author: prashantgupta24

README.md

@@ -1,6 +1,6 @@
 # Activity tracker
 
-[![Go Report Card](https://goreportcard.com/badge/github.com/prashantgupta24/activity-tracker)](https://goreportcard.com/report/github.com/prashantgupta24/activity-tracker)
+[![codecov](https://codecov.io/gh/prashantgupta24/activity-tracker/branch/master/graph/badge.svg)](https://codecov.io/gh/prashantgupta24/activity-tracker) [![Go Report Card](https://goreportcard.com/badge/github.com/prashantgupta24/activity-tracker)](https://goreportcard.com/report/github.com/prashantgupta24/activity-tracker)
 
 It is a libary that lets you monitor certain activities on your machine, and sends a heartbeat at a periodic (configurable) time detailing all the activity changes during that time. The activities that you want to monitor are pluggable services and can be added or removed according to your needs.