language missing in I18nExtendedRef

[Sozialarchiv]

https://github.com/archival-IIIF/presentation-builder/blob/master/src/v3/Base.ts#L11

Otherwise homepage can not have the key language:

https://iiif.io/api/presentation/3.0/#homepage

{
  "homepage": [
    {
      "id": "https://example.com/info/",
      "type": "Text",
      "label": { "en": [ "Homepage for Example Object" ] },
      "format": "text/html",
      "language": [ "en" ]
    }
  ]
}