Update README.md

Author: Zabuzard

README.md

@@ -1,5 +1,6 @@
 # ModernJava
 
+[![codefactor](https://img.shields.io/codefactor/grade/github/together-java/modernjava)](https://www.codefactor.io/repository/github/together-java/modernjava)
 ![Java](https://img.shields.io/badge/Java-19-ff696c)
 [![license](https://img.shields.io/github/license/Together-Java/ModernJava)](https://github.com/Together-Java/ModernJava/blob/master/LICENSE)