Request to add i/o requirements to item properties

[geoff-price]

Like the vision for an ml-model extension. Consider adding requirements for ml inputs and outputs.

Example:

• ml-model: input string REQUIRED. Supported input imagery file type(s) (e.g. GeoTIFF, JPEG, etc.)
• ml-model: output string REQUIRED. Format of vectorized output (e.g. GeoJSON, JSON, geopackage, etc.)