feat(spec): JSON Schema 2020-12 definition for Arazzo descriptions

applied feedback 2024/08/02
applied feedback 2024/08/04
constrain `inputs` to JSON Schema 2020-12 metaschema
applied feedback 2024/08/08 - Step Object constraints on Parameters

closes #176

Co-authored-by: handrews <[email protected]>
Co-authored-by: LasneF <[email protected]>
Co-authored-by: Jason Desrosiers <[email protected]>
Co-authored-by: Frank Kilcommins <[email protected]>