[tracker] publish course to hf.co/learn

[mishig25]

Tracking progress for publishing the course to hf.co/learn

• make necessary doc-builder changes [toc check] Skip readme files doc-builder#490 [toctree] support renaming local doc-builder#491 [notebook conversion] render img outputs doc-builder#492
• Publish course to hf.co/learn:
  • Remove units folder #76
  • bring back french version of the course #77
  • add toctree #78
  • add doc-build workflows #79
  • [hf.co/learn] Intro chapter #80
  • Fix broken imgs link on doc pages #81
  • published at https://huggingface.co/learn/diffusion-course
  • add to search/crawl index

You can checkout https://huggingface.co/learn/diffusion-course