Allow 6.x version of justinrainbow/json-schema

Problem/Motivation

justinrainbow/json-schema is currently added as a core-dev dependency and pinned to the 5.x version
The 6.x version contains several important bugfixes that experience builder will need.

Steps to reproduce

Proposed resolution

Attempt to allow 5.x or 6.x version
The breaking changes between the two versions are here

Remaining tasks

User interface changes

Introduced terminology

API changes

Data model changes

Release notes snippet