add docker run example call

Author: birdayz

README.md

@@ -3,6 +3,12 @@
 
 This sample shows how to build a Javalin microservice and compiling it to native code with GraalVM. I don't expect it to work on anything else than Linux AMD64.
 
+Try it out: 
+```
+docker run -d --init -p 7000:7000 birdy/graal-javalin
+curl localhost:7000
+```
+
 Build either by using Docker and running `docker build .` or directly with Gradle and native-image by running `make build native`.
 
 Find the docker image of this example on [DockerHub](https://hub.docker.com/r/birdy/graal-javalin).