Custom server entry files should allow for omitting the default export

[rossipedia]

I think it would be helpful / intuitive to allow for a custom server entry file to support omitting the default export, falling back to the version that RR supplies when the entry file is missing.

Most apps will likely want to customize error handling (and potentially the new Observability exports), yet don't want to have to maintain the server handler boilerplate.

For example, this would be a valid entry.server.tsx:

import type { HandleErrorFunction } from "react-router";
import * as Sentry from "@sentry/node";

Sentry.init(...);

export const handleError: HandleErrorFunction = (error, args) => {
  Sentry.captureException(error, { extra: { args } });
}

Possible alternatives

Export the default handleRequest from react-router (or possibly a @react-router/defaults package):

export { handleRequest as default } from '@react-router/defaults';
import type { HandleErrorFunction } from "react-router";
import * as Sentry from "@sentry/node";

Sentry.init(...);

export const handleError: HandleErrorFunction = (error, args) => {
  Sentry.captureException(error, { extra: { args } });
}