fix useTransition keys type

Author: jigsawye

types/web.d.ts

@@ -213,14 +213,16 @@ export function useTransition<TItem, DS extends CSSProperties>(
   keys:
     | ((item: TItem) => TransitionKeyProps)
     | ReadonlyArray<TransitionKeyProps>
-    | TransitionKeyProps,
+    | TransitionKeyProps
+    | null,
   values: Merge<DS & CSSProperties, UseTransitionProps<TItem, DS>>
 ): UseTransitionResult<TItem, ForwardedProps<DS>>[] // result array is safe to modify
 export function useTransition<TItem, DS extends object>(
   items: ReadonlyArray<TItem> | TItem | null | undefined,
   keys:
     | ((item: TItem) => TransitionKeyProps)
     | ReadonlyArray<TransitionKeyProps>
-    | TransitionKeyProps,
+    | TransitionKeyProps           
+    | null,
   values: Merge<DS, UseTransitionProps<TItem, DS>>
 ): UseTransitionResult<TItem, AnimatedValue<ForwardedProps<DS>>>[] // result array is safe to modify