Mirror docker-in-docker image

We have started hitting DockerHub's new rate limit due to our cleanup script. Mitigate this by mirroring the docker-in-docker images locally

deps/DindVersion.dhall

+-- Docker-in-Docker image version
+--
+-- We mirror the docker-in-docker images since we tend to pull them often when
+-- iterating on the CI images due to the periodic docker cleanup script run by
+-- the runners.
+--
+-- This file defines which version of the `docker:dind` image we use.
+
+"19.03.14-dind"