Update README.md

add codecov badge

Author: patinthehat

README.md

@@ -4,8 +4,9 @@
     <img src="https://static.permafrost.dev/images/coverage-check/coverage-check-logo-alt.png" alt="coverage-check logo" height="200" style="block">
     <br><br>
     <img src="https://img.shields.io/packagist/v/permafrost-dev/coverage-check.svg" alt="Packagist Version">
-    <img src="https://img.shields.io/github/license/permafrost-dev/coverage-check.svg" alt="license">
+    <img src="https://img.shields.io/github/license/permafrost-dev/coverage-check.svg?" alt="license">
     <img src="https://github.com/permafrost-dev/coverage-check/actions/workflows/run-tests.yml/badge.svg?branch=main" alt="Test Run Status">
+    <img src="https://codecov.io/gh/permafrost-dev/coverage-check/branch/main/graph/badge.svg?token=Xau3YK5548" alt="code coverage">
 </p>
 
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