Just because I’ve noticed you mentioning “adding to the REPL” a few times - I think what you mean to say is adding to the general registry, such that your package can be installed by calling ]add ElementaryChemistry. Every package on GitHub can be “added to the REPL” by its GitHub URL like ]add https://github.com/nilshg/SynthControl, even if its not registered in the general registry.
That said, congrats on your first general registry-registered package!