message: fix(react): add key prop to NotFoundErrorPage route
  Avoids:
  ```
  Warning: Each child in a list should have a unique "key" prop.
  Check the render method of `App`. See for more information.
  in Route
  in App (at src/index.tsx:6)
  ```
diff: @@ -184,7 +184,13 @@ export class PrivateAppImpl implements BackstageApp {
  }
  }
  - routes.push(<Route path="/*" element={<NotFoundErrorPage />} />);
  + routes.push(
  + <Route
  + key="not-found-error-page"
  + path="/*"
  + element={<NotFoundErrorPage />}
  + />,
  + );
  return routes;
  }
  