Matplotlib is not an optional dependency

[olafmersmann]

When installing luxpy 1.12.5 into an empty virtual environment I get

Traceback (most recent call last):
  File "<frozen runpy>", line 189, in _run_module_as_main
  File "<frozen runpy>", line 148, in _get_module_details
  File "<frozen runpy>", line 112, in _get_module_details
  File "/home/olafm/tmp/luxpy-bug/.venv/lib/python3.13/site-packages/luxpy/__init__.py", line 203, in <module>
    from .color import cam
  File "/home/olafm/tmp/luxpy-bug/.venv/lib/python3.13/site-packages/luxpy/color/cam/__init__.py", line 163, in <module>
    from .colorappearancemodels import *
  File "/home/olafm/tmp/luxpy-bug/.venv/lib/python3.13/site-packages/luxpy/color/cam/colorappearancemodels.py", line 175, in <module>
    from .ciecam02 import run as ciecam02
  File "/home/olafm/tmp/luxpy-bug/.venv/lib/python3.13/site-packages/luxpy/color/cam/ciecam02.py", line 35, in <module>
    import matplotlib.pyplot as plt
ModuleNotFoundError: No module named 'matplotlib'

I guess matplotlib should be declared as a required dependency?

Exact steps to reproduce

In an empty directory run

uv add luxpy
echo "import luxpy as lx" > foo.py
uv run python foo.py

Dependency tree

When following the above steps, I get the following dependency tree

luxpy v1.12.5
├── numpy v2.4.2
└── scipy v1.17.0
    └── numpy v2.4.2

when using Python 3.13.11.