Update README.md

Author: conorheffron

README.md

@@ -2,6 +2,8 @@
 
 [![License: GPL v3](https://img.shields.io/badge/License-GPLv3-blue.svg)](https://www.gnu.org/licenses/gpl-3.0)
 
+[![Java CI with Maven](https://github.com/conorheffron/in-mem-cache-sys/actions/workflows/maven.yml/badge.svg)](https://github.com/conorheffron/in-mem-cache-sys/actions/workflows/maven.yml)
+
 ## Run Build & Unit Tests
 ```
 mvn clean package -U