feat(docs): Quarto-generated documentation site

[lukeroantreeONS]

📌 Quarto-generated Documentation for the package

✨ Summary

This PR uses Quarto and Quartodoc to build a documentation website for the package, based on the package docstrings, as well as the markdown and notebook files.

Scope - this PR introduces only the requirements to generate the documentation site, and some updates to typehints / docstrings to facilitate forming the documentation.
A short follow-up PR will introduce the CICD YAML changes to build and deploy to GitHub Pages as part of the release workflow.

📜 Changes Introduced

• feat: quarto-generated documentation site (overall)
• feat: sidebar with sections for different components, and the demos
• fix: make it consistently direct to the landing page (index.qmd) on opening
• chore: make sidebar collapsed by default
• ci: integrate into CICD pipeline, make / update github.io site

✅ Checklist

Please confirm you've completed these checks before requesting a review.

• Code passes linting with Ruff
• Security checks pass using Bandit
• API and Unit tests are written and pass using pytest
• Terraform files (if applicable) follow best practices and have been validated (terraform fmt & terraform validate)
• DocStrings follow Google-style and are added as per Pylint recommendations
• Documentation has been updated if needed

🔍 How to Test

1. Run uv sync to get the additional (dev) packages required
2. Run quartodoc build to build the quarto markdown files
3. Run quarto render to render html documentation site
4. Run quarto preview to locally host the documentation site - explore it in a browser
5. Go to the proof-of-concept GitHub Pages site that I'm temporarily hosting on a fork, verify looks and behaves as the locally hosted one does.