Add typing stub file
Add metadata tests
Add missing dev dependencies
Add merge conflict check pre-commit
Add tox env for py3.9
Update license from MIT to GPL3
Update pyproject with pypi metadata
Update makefile to reduce duplication and add missing targets
Update dependencies to latest versions
Update pre-commit config to piggy back on poetry env
Update pyproject to use poetry-core
Update toxfile to use locked dependencies
Remove unused codeowners file
Remove placeholder test
