docs: add test status badge

Author: leonsteinhaeuser

README.md

@@ -1,5 +1,7 @@
 # k8s-restart-app
 
+[![unit-and-e2e-tests](https://github.com/k8scope/k8s-restart-app/actions/workflows/tests.yaml/badge.svg?branch=main)](https://github.com/k8scope/k8s-restart-app/actions/workflows/tests.yaml)
+
 A simple application that allows to restart services running in K8s. The service that should be allowed to be restarted, must be defined in the configuration file.
 
 ## UI