Create new top-level "overview" section in docs

[mfisher87]

Description

• Front page

  • The front page of our docs is pretty wordy! Extract long-form content to overview section, replace with quick-to-read highlights on the front page. Add some 🔥 emojis.
  • Link to GeoJupyter website on docs front page

• Overview section

  • Add pages/sections: "What is JupyterGIS?", "Roadmap".
  • Move the "features" section from the user guide to the overview.
    • Move the "how-to setup up collaboration" instructions to a new how-tos section in the user guide. Cross-link.

• Link to team compass in contributor guide

• ...?

Checklist

• PR has a descriptive title and content.
• PR description contains references to any issues the PR resolves, e.g. Resolves #XXX.
• PR has one of the labels: documentation, bug, enhancement, feature, maintenance
• Checks are passing.
  Failing lint checks can be resolved with:
  • pre-commit run --all-files
  • jlpm run lint

---

📚 Documentation preview: https://jupytergis--921.org.readthedocs.build/en/921/
💡 JupyterLite preview: https://jupytergis--921.org.readthedocs.build/en/921/lite

[github-actions]

👈 Launch a Binder on branch mfisher87/jupytergis/docs-overview-and-reorg

[github-actions]

Integration tests report: appsharing.space