message: Mounted scene when container did mount
diff: import * as React from 'react';
  -class SceneProxy extends React.Component<{crumb: number}> {
  +class SceneProxy extends React.Component<{crumb: number, mountScene: ({crumb: number, el: HTMLDivElement}) => {}}> {
  private sceneEl: React.RefObject<HTMLDivElement>;
  constructor(props) {
  super(props);
  this.sceneEl = React.createRef();
  }
  componentDidMount() {
  + var {crumb, mountScene} = this.props;
  + mountScene({crumb, el: this.sceneEl.current});
  }
  render() {
  return (
  