Breaking change in signature for resolver function

[csuermann]

Describe the bug
#921 changed the signature of the resolver function from

resolver: Function;

to

resolver: (
    handlersPath: string,
    route: RouteMetadata,
    apiDoc: OpenAPIV3.Document,
  ) => RequestHandler | Promise<RequestHandler>;

This breaks backwards-compatibility as Express request handlers can also be arrays of request handlers.

I believe the signature should instead be

resolver: (
    handlersPath: string,
    route: RouteMetadata,
    apiDoc: OpenAPIV3.Document,
  ) => RequestHandler | Promise<RequestHandler> | Array<RequestHandler> | Promise<Array<RequestHandler>>;

Unfortunately more tweaks seem to be required which I haven't found the time to investigate.