Consolidate path to string map and parameter type

[aaronccasanova]

Hello 👋

While familiarizing myself with the library, I noticed some small opportunities for consolidation:

• Use built-in PropertyKey type instead of string | number | symbol union
• Use .map(String) instead of .map((p) => p.toString())

These updates have no meaningful impact on the behavior or functionality of the library. Therefore, feel free to close this PR if the suggestions are deemed unnecessary 🙂

[benjamind]

While the PropertyKey type change I agree with, I think the other change of using String Constructor for the map argument would be a significant performance cost. I think the constructor is at least an order of magnitude slower than the toString implementation. If you'd like to cleanup the PR to just the PropertyKey change I would be happy to merge though!