titlecase: add package stubs

[Vulwsztyn]

Hi, I created it after the comment from titlecase maintainer. ppannuto/python-titlecase#100 (comment)

I'm guessing this will be preferable for them.

> uv run tests/runtests.py stubs/titlecase --run-stubtest
...
--- success, 1 file checked ---

Running stubtest...
titlecase... (18.43 s) success
Note: titlecase is not currently tested on darwin in typeshed's CI

Regression tests: No test_cases folder for 'titlecase'!


--- TEST SUMMARY: All tests passed! ---

pre-commit Success
Check structure: Success
Pyright: Success
ty: Success
pyrefly: Success
mypy: Success
stubtest: Success
Pyright regression tests: Success
mypy regression test: Success

[Vulwsztyn]

Might I ask for assistance resolving the CI error?

At the same time I'd like to ask if the approach I've taken regarding the conditional import as union is ok.

Actual implementation: https://github.com/ppannuto/python-titlecase/blob/42f43e2de55bf003b286c6f8e8d8b2d26676a167/titlecase/__init__.py#L17

[github-actions]

According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉

[srittau]

Thanks, comments below.

[srittau]

Please add a short comment why these are on the allowlist for posterity.

[srittau]

We prefix type-only symbols in typeshed, i.e. _Pattern in this case. (This should also make the stubtest allowlist entry redundant.)

[srittau]

Same here. Also this should be annotated with @type_check_only (from typing):

@type_check_only
class _CallbackProtocol(Protocol):

[srittau]

Considering that we need to unconditionally import regex in the stubs (and I'm not sure that we can work around this), this should be a regular dependency. While this is not optimal, it only pulls in a type package, so it's not the end of the world.

Suggested change

	optional-dependencies = ["types-regex"]
	dependencies = ["types-regex"]