Hiring coder for parts of publication
You would typically mention this type of help in the acknowledgements section, if at all. It is well understood that developing tooling requires manpower and that there are others on the team aside from the researchers, and it is up to the authors how to acknowledge that assistance. For what its worth, if their contribution was so significant to warrant authorship, that should be a discussion among the research team.

You mention "cite" in your question; this sort of mention would not go in your references, in case that was your thought.