installation: moved from `setup.py` to `pyproject.toml`: - following backend change, installation is now using `pyproject.toml`, and legacy `setup.py` as well as other legacy files have been deleted/updated. - [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. - `VERSION` file has been deleted, in favor or using directly `__version__`, in `libervia/web/__init__.py`. Version can be updated directly from Hatch - update .hgignore - several dependencies version bump, with code update to adapt to changes.