docs: Add SubmitErrorHandler to typescript example so it matches the javascript example

[faysvas]

When browsing the docs I noticed that the TS and JS Sync examples in the docs for handleSubmit were mismatched.

Specifically, even though an onError handler is defined in the TS example, it isn't passed to handleSubmit.

Another idea might be to update both the javascript and typescript examples to include some validation rules, like this one

import React from "react"
import { useForm, SubmitHandler, SubmitErrorHandler } from "react-hook-form"

type FormValues = {
  firstName: string
  lastName: string
  email: string
}

export default function App() {
  const { register, handleSubmit } = useForm<FormValues>()
  const onSubmit: SubmitHandler<FormValues> = (data) => console.log(data)
  const onError: SubmitErrorHandler<FormValues> = (errors) => console.log(errors);

  return (
    <form onSubmit={handleSubmit(onSubmit, onError)}>
      <input {...register("firstName"), { required: true }} />
      <input {...register("lastName"), { minLength: 2 }} />
      <input type="email" {...register("email")} />

      <input type="submit" />
    </form>
  )
}

from the TS section

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