rfc5646grandfathered top-level property

Rule rfc5646grandfathered
final

As defined in RFC5646, grandfathered tags are still allowed but have generally been deprecated in favour of new subtags

Implementation

final rfc5646grandfathered = rule(
  'grandfathered',
  alternatives([
    rule('irregular', alternatives(irregular.map((e) => literal(e)))),
    rule('regular', alternatives(regular.map((e) => literal(e)))),
  ]),
);