Programming

How do you intend to present your GitHub portfolio to your potential employers? Nobody's going to do a full, in-depth, or even basic analysis of your repos unless maybe with automated tools or what GitHub itself provides.

Your CV and interview are much more important. Solutions [and projects] matter much more than details. Experience and that you can talk about your work or experience is much more important than technical details.

A hash table library doesn't sound like particularly noteworthy expertise. Adding a dependency and calling simple documented methods on it in a simple, standard behavior manner isn't noteworthy.

If you're implementing your own, I wonder if "simply" implies a non-noteworthy implementation, or in-depth exploration of hashing and storage indexing. The latter would be a different project though, putting your other on hold.

I don't see it making a difference for employers what you pick here specifically.

If you're interested in implementing one or learning about the technicalities of it go ahead. Otherwise use a library and continue with your project or other interests.

Disclaimer: I'm not in the recruiting space nor do I have that much or recent experience being interviewed/the broader companies hiring processes.