Update README.md

README.md

-Running reg-app in a Docker environment
+# Running reg-app in a Docker environment
 
+A docker image is provided to run a demo version of the reg-app. It can be used as a base to configure and run the reg-app, depending on your needs.
+
+```sh
+mkdir regapp-docker
+cd regapp-docker
+wget 'https://git.scc.kit.edu/reg-app/regapp-docker/-/raw/main/docker-compose.yml'
+docker-compose up
+```
+
+This docker configuration exposes TCP Port 8080 and 9990. On Port 9990 you can reach the wildfly administration console. It is protected with standard credentials. Please change these credentials:
+
+```sh
+docker ps
+docker exec -it <container-id-from-docker-ps> /bin/bash
+/opt/jboss/wildfly/bin/add-user.sh -u admin -p <thenewpassword>
+```
+
+Next, change the reg-app admin password. Visit `http://localhost:8080/admin/user/list-admin-users.xhtml` and choose user 'admin'. Click '+' on the 'Password' panel and set a new password. Choose a hash algorithm if you like.
+
+You should have a running environment now to explore and test. If you want to further expose the reg-app, it is recommended to do so via a reverse proxy.