add status badge for github actions

Author: csviri

README.md

@@ -1,6 +1,8 @@
 # java-operator-sdk
 [![Build Status](https://travis-ci.org/ContainerSolutions/java-operator-sdk.svg?branch=master)](https://travis-ci.org/ContainerSolutions/java-operator-sdk)
 
+![Java CI with Maven](https://github.com/ContainerSolutions/java-operator-sdk/workflows/Java%20CI%20with%20Maven/badge.svg)
+
 SDK for building Kubernetes Operators in Java. Inspired by [operator-sdk](https://github.com/operator-framework/operator-sdk).
 In this first iteration we aim to provide a framework which handles the reconciliation loop by dispatching events to
 a Controller written by the user of the framework.