Ifermi

Fix compatibility with latest spglib.

Enhancements:

* Catch Fermi surfaces and slices that don't cross any bands by utf in https://github.com/fermisurfaces/IFermi/pull/350

What's Changed

The minimum supported Python version is now 3.9.

Enhancements:

- Added support for recent trimesh versions.
- Docs revamped.
- Moved to pyproject.toml instead of setup.py
- Tests moved out of the source folder.

Fixed ``hide_cell`` plotting option.

New features:
- Support for plotting individual bands. Specified using the ``--plot-index`` command line
option. (aj-searle)

Enhancements:
- Fixed high-symmetry points markers.
- Updated dependencies.

Bug fixes:
- Fixed serialization issues.