Add the code coverage badge to the readme

Author: tvbeek

README.md

@@ -2,6 +2,7 @@
 
 [![Latest Version on Packagist](https://img.shields.io/packagist/v/spatie/laravel-binary-uuid.svg?style=flat-square)](https://packagist.org/packages/spatie/laravel-binary-uuid)
 [![Build Status](https://img.shields.io/travis/spatie/laravel-binary-uuid/master.svg?style=flat-square)](https://travis-ci.org/spatie/laravel-binary-uuid)
+[![Code coverage](https://scrutinizer-ci.com/g/spatie/laravel-binary-uuid/badges/coverage.png)](https://scrutinizer-ci.com/g/spatie/laravel-binary-uuid)
 [![Quality Score](https://img.shields.io/scrutinizer/g/spatie/laravel-binary-uuid.svg?style=flat-square)](https://scrutinizer-ci.com/g/spatie/laravel-binary-uuid)
 [![StyleCI](https://styleci.io/repos/110949385/shield?branch=master)](https://styleci.io/repos/110949385)
 [![Total Downloads](https://img.shields.io/packagist/dt/spatie/laravel-binary-uuid.svg?style=flat-square)](https://packagist.org/packages/spatie/laravel-binary-uuid)