Support for nullable references?

[jsoldi]

Hi I'm using @readme/openapi-parser to parse openapi spec. AFAIK this is a valid schema property:

supervisor:
  $ref: '#/components/schemas/Employee'
  nullable: true

Also, when I parse it and inspect the reference, I see that it has a nullable: true property. But its type is ReferenceObject, which is defined like

export interface ReferenceObject {
  $ref: string;
}

Shouldn't ReferenceObject contain a nullable?: boolean property?