Indicate encoding format profile using conformsTo

[stain]

Example: https://by-covid.github.io/baseline-use-case-synthetic-crate/ro-crate-preview.html#vaccines_effectiveness_common_data_model_specification/data/metadata/attributes.csv

 {
  "@id": "attributes.csv",
  "@type": "File",
  "encodingFormat": ["text/csv", {"@id": "https://www.nationalarchives.gov.uk/PRONOM/x-fmt/18"}],
  "conformsTo": {"@id": "https://docs.ropensci.org/dataspice/#create-spice"}
 },
 {
  "@id": "https://www.nationalarchives.gov.uk/PRONOM/x-fmt/18",
  "@type": "WebPage",
  "name": "Comma-Separated Values format (CSV)"
 },
 {
  "@id": "https://docs.ropensci.org/dataspice/#create-spice",
  "@type": "CreativeWork",
  "name": "dataspice CSV profile"
 }

This also adds note to explain conformsTo used on ro-crate-metadata.json and root dataset for profiles (assumes #229)

[stain]

This could use WebPageElement instead of CreativeWork for this particular example, but that depends on #230 and the paragraph is complex enough.

[stain]

Rendered at https://stain.github.io/ro-crate/1.2-DRAFT/data-entities#file-format-profiles

[stain]

Merging without review as call 2023-03-23 agreed to merge all outstanding PR (that are not WIP) so we can do an overall review and push out 1.2.