support json formatted metadata in `runCheck`

[jeanetteclark]

We need to be able to run the FAIR suite over schema.org documents, as outlined in in the parent issue, so all of our metadig libraries need to be able to run checks over json docs. See NCEAS/metadig-r#8 for the R implementation

[rebeccaringuette]

A potentially useful resource is the soso package written in Python, which generates schema.org metadata aligned with the Science-on-Schema.org guidelines for datasets. https://soso.readthedocs.io/en/latest/