AJV option turned on for referencing data in schema

[daviduhlir]

This option will enable to reference data from form to use it in schema. Switch this option to true should not affect anything else.

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• I'm updating documentation
  • I've checked the rendering of the Markdown text I've added
• I'm adding or updating code
  • I've added and/or updated tests
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[heath-freenome]

Closing this because in the upcoming @rjsf v5 release we refactored the ajv 6 validator into its own package @rjsf/validator-ajv6. This package allows you to create your validator with custom ajv options, such as $data thereby giving you more control over how it functions. For more information see PR #2929