static type stubs

[msftcangoblowm]

This package lacks static typing stubs and py.typed (empty) marker file.

Skipping analyzing "caseconverter": module is installed, but missing library stubs or py.typed marker  [import-untyped]

Also refactor the tests into separate /tests/ folder outside of the package. Add __init__.py, conftest.py files. Rename test files, test_ prefix.