Missing Schema Diagram in DANDI Documentation - https://docs.dandiarchive.org

The current DANDI documentation appears to be missing a visual diagram of the DANDI schema.

@yarikoptic @candleindark @kabilar

Start by reviewing the current documentation at https://docs.dandiarchive.org and the dandi-schema repository to determine where schema information is documented. Identify the authoritative schema elements and the appropriate documentation location; done means a clear visual schema diagram is published and linked from the relevant documentation page.

Written by the indexing model from the issue text.