Improve readme of `depth_guided_stable_diffusion` example

[BirgerMoell]

What

• Replaces #5502

Checklist

• [x] I have read and agree to Contributor Guide and the Code of Conduct
• [x] I've included a screenshot or gif (if applicable)
• [x] I have tested the web demo (if applicable):
  • Using newly built examples: app.rerun.io
  • Using examples from latest main build: app.rerun.io
  • Using full set of examples from nightly build: app.rerun.io
• [x] The PR title and labels are set such as to maximize their usefulness for the next release's CHANGELOG
• [x] If applicable, add a new check to the release checklist!

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