Merge pull request #158 from packit/pep561

Make specfile PEP 561 compliant

This allows mypy to recognize specfile type hints in projects importing it and avoids the following error:
Skipping analyzing "specfile": module is installed, but missing library stubs or py.typed marker

Reviewed-by: None <None>

Author: softwarefactory-project-zuul[bot]

setup.cfg

@@ -47,3 +47,6 @@ testing =
 [options.packages.find]
 exclude =
     tests*
+
+[options.package_data]
+* = py.typed