Add support for draft-06

[jdesrosiers]

We need to add support for the following keywords to support draft-06.

items - https://json-schema.org/keyword/draft-04/items
additionalItems - https://json-schema.org/keyword/draft-04/additionalItems
dependencies - https://json-schema.org/keyword/draft-04/dependencies
contains - https://json-schema.org/keyword/draft-06/contains

[Adityakumar37]

@jdesrosiers could you please explain this issue