[readme] Add recommendation to bind host's resolv.conf

[zburgermeiszter]

When containers started BEFORE resolvable starts, those are unable to resolve .docker domains via Resolvable because the Docker daemon uses an old copy of the resolv.conf

If I use the -v /etc/resolv.conf:/etc/resolv.conf:ro to all my docker run command and docker-compose definition, it seems to resolve this issue.

This issue potentially occur when the Docker daemon starts and you use many auto-restarting container where the containers starting in random order.