Better document how to setup DIND custom config
Here https://docs.gitlab.com/ee/ci/docker/using_docker_build.html is described how to setup a DIND setup in the pipeline.
Trying to run it locally I had the necessity of setup a custom MTU. This is not documented. The problem IMHO should be documented here as suggested in https://github.com/docker-library/docker/issues/103#issuecomment-478619847