Document .Names format placeholder in docker-ps man page, fixes
@@ -47,6 +47,7 @@ the running containers.
.Ports - Exposed ports.
.Status - Container status.
.Size - Container disk size.
+ .Names - Container names.
.Labels - All labels assigned to the container.
.Label - Value of a specific label for this container. For example `{{.Label "com.docker.swarm.cpu"}}`
