release.yml add option to publish to TestPyPI

[janosh]

    def test_egg_sources_txt_is_complete():
        """Check that all source and data files in pymatgen/ are listed in pymatgen.egg-info/SOURCES.txt."""
    
        with open(src_txt_path) as file:
            sources = file.read()
    
        # check that all files listed in SOURCES.txt exist
        for src_file in sources.splitlines():
            assert os.path.exists(src_file), f"{src_file!r} does not exist!"
    
        # check that all files in pymatgen/ are listed in SOURCES.txt
        for ext in ("py", "json", "json.gz", "yaml", "csv"):
            for filepath in glob(f"pymatgen/**/*.{ext}", recursive=True):
                if "/tests/" in filepath or filepath.endswith("dao.py"):
                    continue
                if filepath not in sources:
>                   raise ValueError(
                        f"{filepath} not found in {src_txt_path}. check setup.py package_data for outdated inclusion rules."
                    )
E                   ValueError: pymatgen\alchemy\filters.py not found in pymatgen.egg-info/SOURCES.txt. check setup.py package_data for outdated inclusion rules.

tests\test_pkg.py:29: ValueError