It is perfectly fine to ask them here, the worst that can happen is not getting an answer.
To open an issue, just create a github account (it is free, you don’t even have to be “real” in any meaningful sense there). Then go to Issues · lbilli/Jib.jl · GitHub and create a “New issue”. I think asking that package to be registered is a reasonable demand, since it has already a reasonable user-base.