add the actual image

Vladimir Kotal · web-flow · commit d7020238aba2 · 2021-05-20T16:32:02.000+02:00
diff --git a/README.md b/README.md
@@ -59,4 +59,4 @@ There are Slack channels on https://opengrok.slack.com/
 
 You can run OpenGrok as a Docker container as described [here](docker/README.md).
 
-In fact, http://demo.opengrok.org/ is using the Docker image.
+In fact, http://demo.opengrok.org/ is using the `opengrok/docker:master` Docker image.

Original file line number	Diff line number	Diff line change
`@@ -59,4 +59,4 @@ There are Slack channels on https://opengrok.slack.com/`
`59`	`59`
`60`	`60`	`You can run OpenGrok as a Docker container as described [here](docker/README.md).`
`61`	`61`
`62`		`-In fact, http://demo.opengrok.org/ is using the Docker image.`
	`62`	+In fact, http://demo.opengrok.org/ is using the `opengrok/docker:master` Docker image.