Perfomance inprovement for validity

[EECOLOR]

forms/src/components.js

Line 17 in b937d87

const { invalid } = useFormFieldSnapshot(field)

FormFieldValid is now implemented with useSnapshot which means it will render on keystrokes. We could add another hook that prevents these unneeded renders, something like this:

function useFormFieldInvalid(field) {
  const [formFieldInvalid, setFormFieldInvalid] = React.useState(() => snapshot.get(field).invalid)

  React.useEffect(
    () => {
      setFormFieldInvalid(snapshot.get(field).invalid)
      return snapshot.subscribe(field, x => setFormFieldInvalid(x.invalid))
    },
    [field]
  )

  return formFieldInvalid
}