fix: improve useStateValidator and useMultiStateValidator typings.

Now it is compatible with TS 4.x.x

src/useMultiStateValidator.ts

@@ -4,10 +4,10 @@ import { StateValidator, UseStateValidatorReturn, ValidityState } from './useSta
 export type MultiStateValidatorStates = any[] | { [p: string]: any } | { [p: number]: any };
 export type MultiStateValidator<V extends ValidityState, S extends MultiStateValidatorStates> = StateValidator<V, S>;
 
-export function useMultiStateValidator<V extends ValidityState, S extends MultiStateValidatorStates, I extends V>(
+export function useMultiStateValidator<V extends ValidityState, S extends MultiStateValidatorStates>(
   states: S,
   validator: MultiStateValidator<V, S>,
-  initialValidity: I = [undefined] as I
+  initialValidity: V = [undefined] as V
 ): UseStateValidatorReturn<V> {
   if (typeof states !== 'object') {
     throw new Error('states expected to be an object or array, got ' + typeof states);

src/useStateValidator.ts

@@ -1,6 +1,6 @@
 import { Dispatch, SetStateAction, useCallback, useEffect, useRef, useState } from 'react';
 
-export type ValidityState = [boolean | undefined, ...any[]];
+export type ValidityState = [boolean | undefined, ...any[]] | [undefined];
 
 export interface StateValidator<V, S> {
   (state: S): V;
@@ -10,10 +10,10 @@ export interface StateValidator<V, S> {
 
 export type UseStateValidatorReturn<V> = [V, () => void];
 
-export default function useStateValidator<V extends ValidityState, S, I extends V>(
+export default function useStateValidator<V extends ValidityState, S>(
   state: S,
   validator: StateValidator<V, S>,
-  initialState: I = [undefined] as I
+  initialState: V = [undefined] as V
 ): UseStateValidatorReturn<V> {
   const validatorInner = useRef(validator);
   const stateInner = useRef(state);