add containerfile

[rerpha]

Issue

N/A

Description of work

Adds a containerfile based off the python base container which installs all runtime dependencies from pyproject.toml (btw, can we remove requirements.txt if not used? or are they auto-generated?)

I had to pin numpy due to the use of np.unicode_ - numpy 2.0 requires you to use np.str_ instead but I wanted this PR to be fairly fine-scoped. we should probably remove the np.unicode_s and the higher bound pinning in pyproject.toml

BTW, i think it'd be great to update https://hub.docker.com/u/screamingudder when this and the filewriter are ready. I might still have permissions even..

Checklist

• [ x ] Pre-commit hooks have been run (see https://github.com/ess-dmsc/forwarder#developer-information)
• [ x ] Changes have been documented in changes.md