Expose RulesPackageBuilder class in @datasworn/core

[rsek]

A RulesPackageBuilder instance assembles multiple DataswornSource.RulesPackage objects in to a single Datasworn.RulesPackage file. It does so by merging the objects and assigning IDs. It performs some validations that aren't possible with JSON schema.

Datasworn-specific validations

• checks table row dice ranges for coherence against the dice property of their parent OracleRollable
• when provided with an iterable of valid IDs, it checks all ID-type properties for validity, as well as any datasworn ID references made in markdown links or template macros

Notes

• it does not handle read/write operations; if you want to build from JSON/YAML files, you'll need to load + deserialize them first
• it must be provided with some external source of JSON schema validation for both the DataswornSource (incoming data) and Datasworn (outgoing data) schemata.

TODO

The coding side of this is mostly done, but there's some nontrivial documentation outstanding.

• finishing JSdoc annotations for exposed methods/properties
• provide example(s) of use
• (optional) add validation of referenced stats in moves/assets