Add helper type for remote function form enhancement callbacks

Describe the problem

When working with large callback functions, I prefer defining them in the script tag rather than inlining them in the markup. However, I couldn't find a built-in helper type for typing a form enhancement callback.

Creating it manually is no big deal but it would be very nice if I could just import it.

<script lang="ts">
  import { remoteFn } from './example.remote';
  import type { RemoteForm } from '@sveltejs/kit';

  type RemoteFormEnhance<T extends RemoteForm<any, any>> = Parameters<Awaited<T>['enhance']>[0];

  type EnhanceCallback = RemoteFormEnhance<typeof remoteFn>;

  const onSubmit: EnhanceCallback = () => {
    // Lots of code
  };
</script>

<form {...remoteFn.enhance(onSubmit)}>
</form>

Describe the proposed solution

Define helper type internally and export it.

Alternatives considered

No response

Importance

would make my life easier

Additional Information

No response

The issue names RemoteForm, remoteFn.enhance, and the proposed RemoteFormEnhance type; start by locating the existing remote-form type exports and their public entry point. Export the callback helper type so a script-defined onSubmit can be typed and imported from @sveltejs/kit.