Update README.rst
Update README.rst

- https://www.python.org/dev/peps/pep-0518/#json-schema
- https://github.com/pypa/setuptools_scm/blob/master/src/setuptools_scm/config.py#L123
RonnyPfannschmidt/setuptools_scm,RonnyPfannschmidt/setuptools_scm,pypa/setuptools_scm,pypa/setuptools_scm