Add documentation

[bkntr]

Added

• Annotation Viewer controller: add nice text overlay showing the structure under mouse cursor
• Add sample data
• Documentation

Fixed

• Analysis widget: ANOVA shows F value instead of incorrect p value
• Analysis widget: Show ANOVA button now works
• Cell Viewer controller: fix cell colors

[codecov-commenter]

Codecov Report

Attention: 56 lines in your changes are missing coverage. Please review.

Comparison is base (ee27dd8) 78.09% compared to head (7fefb1a) 78.86%. Report is 15 commits behind head on main.

Files	Patch %	Lines
src/napari_brainways/brainways_ui.py	51.02%	24 Missing :warning:
...apari_brainways/controllers/analysis_controller.py	65.11%	15 Missing :warning:
src/napari_brainways/widgets/analysis_widget.py	44.44%	10 Missing :warning:
...inways/controllers/annotation_viewer_controller.py	75.00%	2 Missing :warning:
...brainways/controllers/cell_3d_viewer_controller.py	66.66%	2 Missing :warning:
src/napari_brainways/widgets/workflow_widget.py	84.61%	2 Missing :warning:
...rc/napari_brainways/widgets/registration_widget.py	75.00%	1 Missing :warning:

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #9 +/- ## ========================================== + Coverage 78.09% 78.86% +0.76% ========================================== Files 27 27 Lines 2452 2560 +108 ========================================== + Hits 1915 2019 +104 - Misses 537 541 +4 ```

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