I had trouble deploy this application into heroku after adding ckeditor 5.
The error was like this:
resolve '@ckeditor/ckeditor5-react' in '/tmp/build_f5fca8d3/src/plugins/wysiwyg/admin/src/components/Editor'
remote: Parsed request is a module
remote: using description file: /tmp/build_f5fca8d3/src/plugins/wysiwyg/package.json (relative path: ./admin/src/components/Editor)
remote: Field 'browser' doesn't contain a valid alias configuration
remote: resolve as module