inaccurate error message: adding json with object (rather than array) at top level reports that 'Dataset files must be in CSV format'

[osterbit]

• I guess it should qualify that qri currently requires csv OR json array?
• long-term it would be nice to have a 'subtree selector' gui interface

update:

• looks like this is drag and drop of json files in general, file picker works
• also, file picker will allow me to use that file without complaining, but unable to inspect it after adding