[feature] support of $ref in licence fields

[LasneF]

given we handle a lot of Open API specification given the fact that license are mostly always the same

it would be great that $ref being supported for the field license

this feature is not a breaking change could be added either to moonwalk project or beeing a feature candidate for 3.2.X

following this pattern

license: $ref: ../_shared/license.yaml

this would requires a change in the meta schema

notice that even if license support url , the use case is not really the same...

should be handle the same way as https://github.com/OAI/OpenAPI-Specification/issues/3552