docs: add async to hook snippets to indicate they may return promises (…

…#9426)

documentation/docs/30-advanced/20-hooks.md

@@ -99,7 +99,7 @@ For example, your `load` function might make a request to a public URL like `htt
 ```js
 /// file: src/hooks.server.js
 /** @type {import('@sveltejs/kit').HandleFetch} */
-export function handleFetch({ request, fetch }) {
+export async function handleFetch({ request, fetch }) {
 	if (request.url.startsWith('https://api.yourapp.com/')) {
 		// clone the original request, but change the URL
 		request = new Request(
@@ -124,7 +124,7 @@ If your app and your API are on sibling subdomains — `www.my-domain.com` and `
 /// file: src/hooks.server.js
 // @errors: 2345
 /** @type {import('@sveltejs/kit').HandleFetch} */
-export function handleFetch({ event, request, fetch }) {
+export async function handleFetch({ event, request, fetch }) {
 	if (request.url.startsWith('https://api.my-domain.com/')) {
 		request.headers.set('cookie', event.request.headers.get('cookie'));
 	}
@@ -177,7 +177,7 @@ import crypto from 'crypto';
 Sentry.init({/*...*/})
 
 /** @type {import('@sveltejs/kit').HandleServerError} */
-export function handleError({ error, event }) {
+export async function handleError({ error, event }) {
 	const errorId = crypto.randomUUID();
 	// example integration with https://sentry.io/
 	Sentry.captureException(error, { event, errorId });
@@ -205,7 +205,7 @@ import * as Sentry from '@sentry/svelte';
 Sentry.init({/*...*/})
 
 /** @type {import('@sveltejs/kit').HandleClientError} */
-export function handleError({ error, event }) {
+export async function handleError({ error, event }) {
 	const errorId = crypto.randomUUID();
 	// example integration with https://sentry.io/
 	Sentry.captureException(error, { event, errorId });