docs: generate some flowcharts using the diagrams package

[danceratopz]

🗒️ Description

Adds:

• A new "extras" section to pyproject.tom for dependencies to generate diagrams.
• A jupyter notebook that uses the diagrams package to generate some flowcharts.
• The generated diagrams as png (previews available in PR)..

The diagrams package also offers svg output, but the included icons aren't displayed.

🔗 Related Issues

None

Diagrams

✅ Checklist

• All: Set appropriate labels for the changes.
• All: Considered squashing commits to improve commit history.