Add comprehensive PyUnitWizard showcase notebook

[dprada]

Summary

• add a showcase Jupyter notebook that walks new users through configuring, converting, and validating PyUnitWizard quantities across libraries
• register the new notebook in the Showcase table of contents

Testing

• jupyter nbconvert --to notebook --execute --inplace docs/contents/showcase/PyUnitWizard_Showcase.ipynb

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https://chatgpt.com/codex/tasks/task_e_68d6d31728588326954cdaa5eb0c59d3

[Copilot]

Pull Request Overview

This PR adds a comprehensive Jupyter notebook to showcase PyUnitWizard functionality for new users. The notebook demonstrates core features like configuring unit libraries, creating quantities, converting across forms and units, validating dimensions, working with arrays, and accessing physical constants.

• Introduces a comprehensive tutorial notebook with examples across multiple unit library backends
• Registers the new showcase notebook in the documentation table of contents
• Provides executable examples for configuration, conversion, and validation workflows

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
docs/contents/showcase/index.rst	Adds the new PyUnitWizard showcase notebook to the documentation table of contents
docs/contents/showcase/PyUnitWizard_Showcase.ipynb	Creates a comprehensive tutorial notebook demonstrating PyUnitWizard features with executable examples

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 72.23%. Comparing base (4be236b) to head (1d19137).
⚠️ Report is 2 commits behind head on main.
✅ All tests successful. No failed tests found.