Add an inheritance example (`allOf` + `$ref`), not just composition

[LukasOro]

examples/PersonWithAddress.schema.json demonstrates composition (embeds Address via $ref + scoped @context) but there is no inheritance example using allOf + $ref to a parent schema (e.g. Employee extends Person).

This is the most-requested "object-oriented" capability and currently has no worked example.

Ask — add examples/:

• Employee.schema.json with allOf: [{ $ref: Person.schema.json }] and a @context array that
  imports the parent context, plus its own terms.
• an instance (e.g. alice.json) and the expected RDF (Turtle) output.

Acceptance: new files build/validate and (ideally) load in the playgrounds.