Add surface sample data

[jo-mueller]

Relevant for #376 - adds cells3d data example from https://github.com/haesleinhuepf/napari-process-points-and-surfaces demo notebooks

Long description

This pull request introduces a new sample data function, cells3d_curvatures, to the napari_clusters_plotter package, along with corresponding updates to the package's exports, tests, and plugin configuration. The changes primarily focus on adding support for loading and visualizing 3D mitotic nucleus surface curvatures in Napari.

New Feature: cells3d_curvatures Sample Data

• New function implementation: Added the cells3d_curvatures function in _sample_data.py to load 3D mitotic nucleus surface curvatures, including vertices, faces, and nucleus images. The function returns layer data tuples for visualization.
• Exported in __init__.py: Updated the __all__ list to include cells3d_curvatures, making it accessible as part of the public API.

Plugin Configuration Updates

• Plugin contributions: Added a new entry for cells3d_curvatures in the contributions section of napari.yaml, enabling it as a sample data loader in the Napari plugin.
• Menu integration: Added a corresponding menu item for cells3d_curvatures in the napari.yaml file, allowing users to load this dataset via the Napari interface.

Testing Enhancements

• Parameterized testing: Updated the sample data tests in test_sample_data.py to use pytest.mark.parametrize, ensuring both bbbc_1_dataset and cells3d_curvatures are tested for proper functionality.