Issue #18: Added Codecov badge

Signed-off-by: alexmerlin <[email protected]>

Author: alexmerlin

README.md

@@ -9,6 +9,7 @@
 [![GitHub license](https://img.shields.io/github/license/dotkernel/dot-cli)](https://github.com/dotkernel/dot-cli/blob/3.0/LICENSE)
 
 [![Build Static](https://github.com/dotkernel/dot-cli/actions/workflows/static-analysis.yml/badge.svg?branch=3.0)](https://github.com/dotkernel/dot-cli/actions/workflows/static-analysis.yml)
+[![codecov](https://codecov.io/gh/dotkernel/dot-cli/graph/badge.svg?token=0DFCK2GUBT)](https://codecov.io/gh/dotkernel/dot-cli)
 
 [![SymfonyInsight](https://insight.symfony.com/projects/b9489f03-14e3-441f-aefd-e3b549b4917e/big.svg)](https://insight.symfony.com/projects/b9489f03-14e3-441f-aefd-e3b549b4917e)