Add coverage status badge to README

Author: chrisjwelly

README.md

@@ -1,6 +1,8 @@
 # chahan
 NUSSU Logistics Booking Application, Iteration 2
 
+[![Coverage Status](https://coveralls.io/repos/github/commit-tech/chahan/badge.svg?branch=add-coveralls-to-project)](https://coveralls.io/github/commit-tech/chahan?branch=add-coveralls-to-project)
+
 # Installation
 This project uses Rails 6.0.0 and Ruby 2.6.3p62