support for stub-only packages

[jorenham]

From the looks of it, there is no support for checking stub-only packages. Because when I run it as

uv run pytype scipy-stubs

or

uv run pytype scipy-stubs/__init__.pyi

in the scipy/scipy-stubs repo, (after installing pytype of course), I get

usage: pytype [options] input [input ...]
pytype: error: Need an input.

It doesn't matter whether I add a config to pyproject.toml or not.