Add frozendict signature (Python 3.15 compatibility)

[befeleme]

Fixes #623

[hunterhogan]

I added your fix to https://github.com/hunterhogan/Z0Z_tools. I'm not trying to replace toolz\cytools: I'm trying to help the maintainers catch up with the mountain of mundane improvements the packages need. I hope that if enough people contribute to https://github.com/hunterhogan/Z0Z_tools and we demonstrate that the codebase is good, the pytoolz maintainers will take over the updated codebase we create.

Therefore, if you were to participate on https://github.com/hunterhogan/Z0Z_tools, that would be wonderful and greatly appreciated.

[hunterhogan]

In toolz.dicttoolz functions with a factory parameter, builtins.frozendict will not work in most or any of the functions. 😦 I haven't surveyed the impact on itertoolz or the other modules yet.

I assume that if I open an Issue here in toolz, 73 different AI agents will submit PRs.