message: fix: use spread instead of explicit Object.assign for IE11 support
diff: @@ -172,8 +172,8 @@ export const ValidationObserver = (Vue as withObserverNode).extend({
  return;
  }
  - this.refs = Object.assign({}, this.refs, { [subscriber.vid]: subscriber });
  - this.refsByName = Object.assign({}, this.refsByName, { [subscriber.name]: subscriber });
  + this.refs = { ...this.refs, ...{ [subscriber.vid]: subscriber } };
  + this.refsByName = { ...this.refsByName, ...{ [subscriber.name]: subscriber } };
  if (subscriber.persist) {
  this.restoreProviderState(subscriber);
  }
  