- Improve the build of the image by introducing `build.sh`.
  It can be used with `podman` or `buildah` and
  also provides a way of building a `dev` or `prod`
  image for development purposes by
  `build.sh [dev|prod]`.

- CI runs this script as well with `buildah`.

Signed-off-by: Gabriel Nützi <gnuetzi@gmail.com>