Update README.md

Author: jviide

README.md

@@ -8,6 +8,8 @@
 $ docker run -ti --rm -p 8080:8080 --cap-add NET_ADMIN hownetworks/tracetrout
 ```
 
+The above Docker image doesn't support IPv6. Use the `hownetworks/tracetrout:ipv6` image if you're feeling adventurous and want to [work with Docker and IPv6](https://docs.docker.com/config/daemon/ipv6/).
+
 ## A Less Quick Start
 
 ### Prerequisites