When creating containers to run a single one-off command that alters a
volume, the `--rm` option is needed, otherwise that container is left
around and can cause confusion later on.
https://github.com/albertito/chasquid/pull/69
Amended-by: Alberto Bertogli <albertito@blitiri.com.ar>
Adjusted commit message.
This patch adds a new docker directory, which contains a Dockerfile plus
some additional configuration for creating a container that runs
chasquid+dovecot+letsencrypt.
It also updates the gitlab CI pipeline to automatically build and
publish an image on each commit.
This is experimental and likely to break.
