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.

Beginne damit, die bestehende referencing.Registry-Schnittstelle und die Erstellung von referencing.jsonschema-Ressourcen rund um DRAFT7.create_resource zu lesen. Vergleiche das Verhalten der vorgeschlagenen SchemaValidatingRegistry mit DraftNValidator.check_schema und bestimme, wie die konfigurierbare Metaschema-Suche funktionieren sollte; abgeschlossen ist es, wenn das Einfügen Ressourcen validiert und ungültige Schemas zurückweist, ohne die Registry-Schnittstelle zu beeinträchtigen.