Build docker image

[Bone Baboon]

I am trying to build a docker image.

I have added `docker` and `docker-cli` to my system configuration and
reconfigured the system.  The `docker` command needs a docker daemon
running.

I have added the docker service to the system configuration file with
`(service docker-service-type)` in the list of services.  When I try to
reconfigure the system I get this error message "guix system: error:
service 'dockerd' requires 'networking', which is not provided by any
service".