chore(async-stack): make prop type generic optional

Author: vnphanquang

.changeset/clean-carpets-fetch.md

@@ -0,0 +1,5 @@
+---
+'@svelte-put/async-stack': patch
+---
+
+make Resolved generic param to StackItemProps optional

packages/async-stack/src/types.public.d.ts

@@ -3,7 +3,7 @@ import type { Component, ComponentProps } from 'svelte';
 
 import type { StackItem } from './stack-item.svelte.js';
 
-export interface StackItemProps<Resolved> {
+export interface StackItemProps<Resolved = undefined> {
 	/** the stack item instance injected by the stack */
 	item: Omit<StackItem<Component<StackItemProps<Resolved>>, Resolved>, '#internals'>;
 }