Simon stylesheet changes

• Marks qutil/plotting/stylelib/*.mplstyle as project files (they are included in the python package)
• Create stylelib install function install_styles in qutil.plotting
• Create a script that runs this function automatically by hatch autorun i.e. it will run when/before qutil is imported for the first time.
• Editable installs are deteced via qutil's path and symlinks are used in that case.

Open questions/problems:

• Matplotlibs stylesheets are per user, not per virtual environment! Multiple versions of qutil in seperate venvs will interfere with each other.
• Should we overwrite existing stylesheets?

TODO:

• Put editable install detection in qutil itself ( nice utility function;) )
• Document install_styles properly
• Do not overwrite stylesheets. Maybe include a version/path tag on install?

Still untested.