Support donate property in OAS registry

OAS registry spec has been updated to support a `donate` url property in packages. See https://github.com/open-audio-stack/open-audio-stack-registry/issues/73

OwlPlug already contains UI feature to redirect to a donation website. This property must be consumed from OAS source kind.