Use Case: Link to and re-use existing metadata (sidecar) files

[eocarragain]

As a researcher who already uses a defined metadata standard/serialisation, I want to be able to reuse this metadata and have RO-Crate express its relationship to the dataset as a whole and/or parts of the dataset (a directory or set of files), so that I can easily layer RO-Crate on top of my existing workflow and community/disciplinary norms

Examples: I have an existing side-car file for describing tabular data and don't want to have to sync that into RO-Crate syntax, but want RO-Crate to express the relationship between the tabular data file and the sidecar file, see BIDS handling of tabular data

See, in contrast, #27 where variable-level metadata is captured directly in RO-Crate metadata

[eocarragain]

This may also be a more generalized form of #19, i.e. how to reflect more specific metadata formats contained in the RO-Crate (e.g. MIAME)