consider switching from toml to tomli

[graingert]

pip is moving from toml to tomli pypa/pip#10035 setuptools_scm should consider following suit

• pip: Replace vendored toml with tomli for TOML v1.0.0 compat pip#10035
• build: Consider switching to TOML v1 compliant parser build#308
• black: Switch toml TOML library for tomli psf/black#2301

[RonnyPfannschmidt]

Thanks for the note, will do asap