- Use CMD instead of ENTRYPOINT to launch sshd (easier to overwrite when
using locally).
- Expose port 22.

Installed from their repository.

For checking the deployment.

Needed headers for some Python packages.

There's no need to run it in a specific runner, but I did because I
set tags on the runners but didn't set them to run untagged (fixed in
gitlab-runner-docker@dfc42dda).

Those hooks fail because we run pre-commit inside of a Docker container
(see https://github.com/pre-commit/pre-commit/issues/1387).

Setup pre-commit and add it to CI. Correct a few things as well.

Pull a new image and build without caching. I want updates for existing
packages without changing files.

- Image with Debian, Python and Golang packages installed.
- Deployment with Docker Compose and GitLab CI.

Standard stuff, really.