Consider adding `referencing.jsonschema.SchemaValidatingRegistry`

It might be a nice convenience to have an object with the same interface as referencing.Registry but which automatically validated schemas (Resources) on insertion.

Specifically an object where (in pseudocode):

import referencing.jsonschema

valid_schema = referencing.jsonschema.DRAFT7.create_resource({"type": "integer"})
invalid_schema = referencing.jsonschema.DRAFT7.create_resource({"type": 37})

registry = referencing.jsonschema.SchemaValidatingRegistry()
valid_schema @ registry  # fine
invalid_schema @ registry # -> big boom!

This would be an inverted dependency on jsonschema (the library) -- because we'd call DraftNValidator.check_schema each time a resource was added to the SchemaValidatingRegistry.

We should likely allow for parametrizing looking up the right object for validation (i.e. fetching which metaschema to use and what function to call with it), especially considering that this library (referencing) is meant to be JSON Schema implementation agnostic.

Start by reading the existing referencing.Registry interface and referencing.jsonschema resource creation around DRAFT7.create_resource. Compare the proposed SchemaValidatingRegistry behavior with DraftNValidator.check_schema and determine how configurable metaschema lookup should work; done means insertion validates resources and rejects invalid schemas without breaking the registry interface.