mention docker image

Vladimir Kotal · web-flow · commit 40e6c66ecf2b · 2018-12-27T14:08:05.000+01:00
diff --git a/README.md b/README.md
@@ -56,3 +56,5 @@ There are also Slack channels on https://opengrok.slack.com/
 ## 6. Demo
 
 Visit <http://demo.opengrok.org>
+
+Anyway, just demo it yourself - there are Docker images available on https://hub.docker.com/r/opengrok/docker/
