Provide examples of AJV JSON schema validation with Datasworn

[rsek]

• show validation of an entire RulesPackage object
• show validation primary/embeddable node types individually (and, ideally, for any subschema in definitions)
• show how to insert defaults when validating
• provide a config object -- or even a separate package with an AJV dependency, that serves as a friendlier wrapper?
• what should people who only need one major category of schemas (e.g. oracles) do? it's a big schema!