Pass submit function to useForm composable

[ayZagen]

First of all, thanks for your support and great work.

Currently we provide form submit handler by passing it to handleSubmit function returned from useForm composable. Instead of calling it as a separate function, having a property in useForm argument would be more straightforward.

To give an example, instead of doing like this:

const { handleSubmit } = useForm( );

const onSubmit = handleSubmit( async ( values, ctx) => {
// ... submit logic
})

something like the following would be better for dx and will be more related to usage of useForm composable:

const { submitForm } = useForm({
  handleSubmit: async (values, ctx) => {
    // ... submit logic
  }
});

In order to prevent featuring this as a breaking change, the both ways could be available without contradicting each other.

Assuming the new interface is like the one above, following would work without any breaking change:

const { submitForm, handleSubmit } = useForm({
  handleSubmit: async (values, ctx) => {
    console.log('initial submit')
  }
});

const onSubmit = handleSubmit(async (values, ctx) => {
  console.log('overridden')
})

// onSubmit() // Prints: overridden
submitForm() // Prints: overridden