New dind creates large volumes that need to be cleaned up regularly

[buehlefs]

The official dind image creates a volume that can be quite large and is not cleaned up with the container.
This can easily fill up all the space allowed for the docker VM resulting in spurious and hard to track errors.
A regular cleanup can prevent this and should be added to troubleshooting and stopping the docker compose sections of the docs.

# cleanup all dangling resources (volumes, containers, etc.)
docker system prune

# optinally cleanup unused images
docker image prune