- updated installation to use the now standard `pyproject.toml` instead of legacy
`setup.py`. `setup.py` and other legacy files have been deleted.
- removed outdated README4PACKAGERS
- removed pylintrc which has not been correctly reviewed. Linter conf should go to
`pyproject.toml` now.
- [hatch](https://hatch.pypa.io) is now used as main building tool. However, thanks to the
use of standards, other tools can be used too.
- update .hgignore
- several dependencies version bump, with code update to adapt to changes.
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