Forked from original repository.
Fixed objects extension that were cached during dereferencing.
Reason why pull request was not made is because:
that extended objects are not allowed by the JSON Schema or JSON Reference specs. The json-schema-ref-parser library only supports them for backward-compatibility, and it's possible that this support will be removed at some point in the future to bring this library inline with the official spec (https://github.com/APIDevTools/json-schema-ref-parser/issues/92).