Add reset function to useFetcher object to support modal usage

[cblauvelt]

I am using useFetcher to submit form data without navigation within a modal. When a user submits data within the modal and closes the modal I would like clear the fetcher state so when the user re-opens the modal they get the same experience as the first usage.

I can work around this by rendering the modal only when needed which mounts and unmounts the modal component but this seems sub-optimal. Ex:

{modalOpen ? (<ModalComponent />) : null }

See discussion at remix-run/remix#2749.