Update controlnet example readme

[BirgerMoell]

What

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: app.rerun.io
  • Using examples from latest main build: app.rerun.io
  • Using full set of examples from nightly build: app.rerun.io
• 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
• Docs preview
• Examples preview
• Recent benchmark results
• Wasm size tracking

[github-actions]

Size changes

Name	main	5490/merge	Change
incremental_logging.rrd	(none)	0.0 MiB	+100%

[nikolausWest]

Some things to fix but generally good!

[nikolausWest]

Alright, @BirgerMoell, this looks good to me now. You just need to take it home by making the PR pass.

• Spellcheck looks like you need to add some words to cspell.json
• You need to check the relevant checkboxes on the PR