Build failure / Vaadin 14.8.1

Executing the demo with mvn jetty:run fails with
```
ERROR in J:\fc\addons\fc-addons-demos-14\node_modules\@types\express-serve-static-core\index.d.ts
[tsl] ERROR in J:\fc\addons\fc-addons-demos-14\node_modules\@types\express-serve-static-core\index.d.ts(99,68)
      TS1110: Type expected.
```
