message: Updated ref implementation
diff: @@ -4,7 +4,11 @@ import withSharedElementRegistry from './withSharedElementRegistry';
  import { SharedElementProps } from './Props';
  class SharedElement extends React.Component<SharedElementProps, any> {
  - private ref: HTMLElement;
  + private ref: React.RefObject<HTMLElement>;
  + constructor(props) {
  + super(props);
  + this.ref = React.createRef();
  + }
  componentDidMount() {
  this.register();
  }
  @@ -20,16 +24,16 @@ class SharedElement extends React.Component<SharedElementProps, any> {
  sharedElementRegistry.unregisterSharedElement(scene, this.props.name);
  }
  register() {
  - if (!this.ref) return;
  + if (!this.ref.current) return;
  var {unshare, name, data, stateNavigator, sharedElementRegistry} = this.props;
  var scene = stateNavigator.stateContext.crumbs.length;
  if (!unshare)
  - sharedElementRegistry.registerSharedElement(scene, name, this.ref, data);
  + sharedElementRegistry.registerSharedElement(scene, name, this.ref.current, data);
  else
  - sharedElementRegistry.unregisterSharedElement(scene, name, this.ref);
  + sharedElementRegistry.unregisterSharedElement(scene, name, this.ref.current);
  }
  render() {
  - return React.cloneElement(this.props.children, {ref: el => this.ref = el});
  + return React.cloneElement(this.props.children, {ref: this.ref});
  }
  }
  