Enable client installation via pip

[jakob1379]

Based on the discussion linked below, updating the project definition in pyproject.toml may eliminate the need to build and manually package root-painter for distribution. This could enable direct installation of the root-painter GUI to the system launcher via pip install. Windows compatibility requires verification, but this simplifies user installation.

https://discuss.python.org/t/whats-the-status-of-scripts-vs-entry-points/18524/9

The files specified in scripts will end up in the wheel as-is at <project>-<version>.data/scripts/... These will end up in the bin directory of a Python virtual environment.

The entry_points specified in console_scripts will end up in a .txt file in the metadata folder (.dist-info) within the wheel. The latter get launcher files generated for them by the installer (i.e. pip) in a cross-platform manner.

This change could also remove the need to build a deb package, potentially broadening availability to system launchers beyond Debian.

[Abe404]

For many users, the command line can is more complicated. So I'd argue that 'simplify' is subjective here.
I certainly think it could improve improve the situation for linux users. I'd be happy for this to be the default for linux users, and I would not be against it being an option for other OS's but I don't think it's a viable alternative to the GUI installers for all users.