Let PiHole play nice with docker-compose

When you run pihole in a docker container, it could be difficult to build images on the same docker daemon, because docker-compose cannot pass DNS request to another container during build, and normal dns resolution fixes won't work.

I solved this issue reading this article and configuring my docker daemon to use a public DNS service:

sudo cat /etc/docker/daemon.json 
{
"dns":["1.1.1.1"]
}