Update Usage.md

[olilarkin]

What is the problem or limitation you are having?

It seems that maybe a recent switch to a different package layout with the xcframework has made the Usage.md instructions obsolete? I was able to use PythonKit without the module map but it is unclear to me now how i install dependencies since the xcframework contains the site packages folder.

Describe the solution you'd like

update about how it's meant to work

Describe alternatives you've considered

ditto

Additional context

thanks for this cool project!

[freakboy3742]

Support for PythonKit is provided on a "best effort" basis; we're happy to incorporate changes to documentation, but we're not actively monitoring for changes.

FWIW, the Briefcase iOS template gives the paths that are used by the new project layout:

NSString *resourcePath = [[NSBundle mainBundle] resourcePath];
NSString *python_home = [NSString stringWithFormat:@"%@/python", resourcePath, nil];
NSString *stdlib_path = [NSString stringWithFormat:@"%@/lib/python3.13", python_home, nil];
NSString *libdynload_path = [NSString stringWithFormat:@"%@/lib/python3.13/lib-dynload", python_home, nil];

I think that is all the detail you need to adapt the current usage guide; if you want to convert that into a PR updating USAGE.md, I'll happily merge those changes.