Gwsumm

Minor release to address the following items:
- Drop support for python versions less than 3.9
- Migrate package build to pyproject.toml, removing setup.cfg, versioneer, etc.
- Clean up and improve documentation, update readthedocs configuration
- Bugfix for the combined V x T calculation for multiple detectors
- Update axes.grid keyword value that had been deprecated
- Add density option for histograms

For a full record of changes relative to the release, see https://github.com/gwpy/gwsumm/compare/2.1.7..2.2.0.

Point release to address the following items:
- Add / update mappings for when not all of the requested interval is covered by aggregated h(t) frames
- Improve the archiving of HDF5 to be more robust to corruption
- Bugfix for when hours are requested in a state

For a full record of changes relative to the release, see https://github.com/gwpy/gwsumm/compare/2.1.6..2.1.7.

Point release to make the reading of an HDF5 archive file more robust against corrupted files.

For a full record of changes relative to the release, see https://github.com/gwpy/gwsumm/compare/2.1.5..2.1.6.

Point release to support specifying inspiral range calculation method

For a full record of changes relative to the release, see https://github.com/gwpy/gwsumm/compare/2.1.4..2.1.5.

Point release to fix a problem when testing trigger files for zero length and removing them from the cache.

For a full record of changes relative to the release, see https://github.com/gwpy/gwsumm/compare/2.1.3..2.1.4.

Point release to publish a workaround for zero length trigger files not being able to combine using `EventTable.read()`

For a full record of changes relative to the release, see https://github.com/gwpy/gwsumm/compare/2.1.2..2.1.3.