More multimodal datasets docs (#1641)
* more multimodal datasets docs
* minor
* add to toc
* mention in data files page
* Apply suggestions from code review
Co-authored-by: Daniel van Strien <davanstrien@users.noreply.github.com>
* link to storage recommendations and limits for the image files cases
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Co-authored-by: Daniel van Strien <davanstrien@users.noreply.github.com>
