- make the package python 3.6+ only as it dropped support
for older versions

- Update to version 1.0.0 (2022-05-26)
Remove sphinx.util.force_decode. Previously we hacked it in to support Python 2 and Sphinx 3.x, but Sphinx 4.0 deprecated it and dropped Python 2 support.
Replace Travis-CI with GitHub Actions
Add support for Python 3.6, 3.7, 3.8, 3.9, 3.10, and PyPy3.
Drop support for Python 2.7, 3.3, 3.4, 3.5, and PyPy.
Update to work with newer Sphinx versions:
Sphinx.domains -> Sphinx.registry.domains
Sphinx.override_domain(D) -> Sphinx.add_domain(D, override=True)
Drop support for Sphinx < 4.0.