Shorten and unify in-example description markdowns

[nikolausWest]

The in-app markdown description can be a great way to share some context about what you're looking at for someone that opened an example without a deep understanding of what that is. It isn't a good place for a tutorial / deeper description since the in-app markdown documents provide a much worse reading experience than our website.

Example:

We should unify these in app markdown descriptions to:

• Be much shorter and just give enough information to orient someone who opened an example on app.reru.io without much context.
  • They need to know that this is an example recording of X, built using Rerun.
  • It should link to some key pieces of data in the recording
  • Link to documentation and the source code
• Each example we include on app.rerun.io should have a markdown description

[emilk]

My work-list:

• arkit_scenes
• detect_and_track_objects
• dicom_mri
• dna
• human_pose_tracking
• nuscenes
• open_photogrammetry_format
• plots
• raw_mesh
• rgbd
• rrt-star
• segment_anything_model
• structure_from_motion