fix: add a cleanup function to useEffect that loads data from storage.

[mkhennoussi]

Hi !

This fixes the issue with data not loaded from the storage as the Effects are fired twice in dev: https://beta.reactjs.org/learn/synchronizing-with-effects#how-to-handle-the-effect-firing-twice-in-development

It simply creates a cleanup function that wirte to the storage after reading it.

Should fix: #18

Hope it helps !

[BorjaRafolsMartinez]

This actually makes this plugin work with defaultValues option from react-hook-form

[Alain1405]

I can confirm with this fix the form values are persisted even when defaultValuea is passed to useForm. Without this defaultValues overrides the persisted state.
An alternative solution would be to pass defaultValues directly to useFormPersist