Particle

- `Particle` class:
- Literals now defined for all particles in the loaded "database" CSV file, excluding nuclei.
- Defined and/or fixed the programmatic names for diquarks and SUSY particles.
- Data CSV files:
- Version 9 of package data files, with all antiparticle bars done with `\overline` instead of `\bar`.
- Miscellaneous:
- Added `latex_name_unicode()` function to convert in particle names in LaTeX all greek letters by their unicode.
- Added a `.zenodo.json` file to provide enhanced metadata for Zenodo.
- CI updates for newer versions of Black and pre-commit.

- Code refactored in the CI by Sourcery.ai.
- Updates to versions of pre-commit hooks.

- `Particle` class:
- Methods `Particle.to_list` and `Particle.to_dict` enhanced.
- Data CSV files:
- Version 8 of package data files, with fixed parities for antibaryons with undefined parity.
- Tests added to check if every particle is parsed and loaded correctly.
- Miscellaneous:
- Minor fix on static typing.

- PDG ID:
- Minor simplifications in some PID functions.
- `Particle` class:
- Test for `Particle.is_unflavoured_meson` added.
- Miscellaneous:
- Full static typing implemented.

- Dependencies:
- hepunits >= 2.0.0.
- Tests:
- CI updates.
- Tests adapted to hepunits 2.0.0.
- Miscellaneous:
- Support for Python 3.9 added.

- `Particle` class:
- `Particle.dump_table()` method removed and replaced with methods
`Particle.to_dict()` and `Particle.to_list()` (avoids strong coupling of packages).
- Improve LaTeX particle names with `\prime` in them,
to have correct HTML names for such particles.
- Misleading/awkward `Particle.__int__` method removed.
- `PDGID` class:
- New functions for qualification of PDG IDs:
- `is_quark`.
- `is_gauge_boson_or_higgs`.
- `is_sm_gauge_boson_or_higgs`.
- `is_generator_specific`.
- `is_technicolor`.
- `is_composite_quark_or_lepton`.
- `is_special_particle`.
- Several PDG ID qualification functions improved and/or enhanced,
and minor bugs fixed for certain special particles.
- Data CSV files:
- Version 7 of package data files, with fixed LaTeX and HTML particle names.
- Added newly-ish defined particles for two-Higgs-doublet scenario
and additional SU(2)xU(1) groups.
- Internal and user-irrelevant file `particle2008.csv` file removed.
- Tests:
- Test suite extended to deal with new PDG ID related functions.
- Documentation:
- Demo notebook slightly extended.
- More explanations in the functions qualifying PDG IDs.
- Miscellaneous:
- LaTeX-to-HTML particle name conversion function fixed to correctly
deal with names containing `\prime` and/or `\tilde`.