Add inline markdown example description to public examples

[emilk]

What

• Closes Shorten and unify in-example description markdowns #5440

All main and nightly examples now include an inline markdown description. I made sure it is not too long. I've adjusted the blueprints where suitable.

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 newly built examples: rerun.io/viewer
  • 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!

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

[github-actions]

Deployed docs

Commit	Link
3e86db5	https://landing-58ogt4f8d-rerun.vercel.app/docs

[Wumpf]

neat!