Move .json examples to validation/

[brendanreardon]

Feature description

@korikuzma recommended that we move examples from schema/cat-vrs/json to validation/, similar to what VRS does. She further recommended adding a Testing section to the root README that details this. For example:

Validation tests (in validation/) provide language-neutral tests for those implementing tools with Cat-VRS.

Tasks for this Issue:

• Update make file under schema/ to place example json files to validation/
• Update make file under schema/ to ... not produce example .rst files?
• Update json points within readthedocs to these json files

Contribution

None

[korikuzma]

@brendanreardon You could also consider moving them to the current examples directory (might be better since you already have examples there). IMO just taking them out of the schema directory is nice.