Rehaul 'how to integrate your library' docs (huggingface#1442)

* Rehaul 'how to integrate your library' docs

* Apply suggestions from code review

Co-authored-by: Omar Sanseviero <[email protected]>

* consistency

* style

* better

* code style

* useless picture

* Suggestion from @NielsRogge

* Update docs/hub/models-adding-libraries.md

Co-authored-by: vb <[email protected]>

* VFIMamba instead of Grok-1

* fix url

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Co-authored-by: Omar Sanseviero <[email protected]>
Co-authored-by: vb <[email protected]>

Author: 3 people