Add an how-to guide for the map view

[abey79]

What

How-to guide for the map view.

Spirit:

• information dense (no super-basic tutorial material)
• easy to maintain (no snippets/screenshots)

Checklist

• I have read and agree to Contributor Guide and the Code of Conduct
• I've included a screenshot or gif (if applicable)
• I have tested the web demo (if applicable):
  • Using examples from latest main build: rerun.io/viewer
  • Using full set of examples from nightly build: rerun.io/viewer
• The PR title and labels are set such as to maximize their usefulness for the next release's CHANGELOG
• If applicable, add a new check to the release checklist!
• If have noted any breaking changes to the log API in CHANGELOG.md and the migration guide

• PR Build Summary
• Recent benchmark results
• Wasm size tracking

To run all checks from main, comment on the PR with @rerun-bot full-check.

[github-actions]

Latest documentation preview deployed successfully.

Result	Commit	Link
✅	46fe8e4	https://landing-jas9x0ecy-rerun.vercel.app/docs

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[jleibs]

This is nice.

The one thing missing in my opinion is a mention of the MapView blueprint class