Try to fix server-bundle

Author: alexeyr

spec/dummy/client/app/packs/server-bundle.js

@@ -2,6 +2,7 @@
 import './../generated/server-bundle-generated.js'; // eslint-disable-line import/extensions
 // Shows the mapping from the exported object to the name used by the server rendering.
 import * as ReactOnRails from 'react-on-rails';
+globalThis.ReactOnRails = ReactOnRails;
 // Example of server rendering with no React
 import HelloString from '../non_react/HelloString';