docs: fix helloWorldLoader function definition (#8429)

- Make helloWorldLoader async to follow the type definition

Closes #8428

www/apps/book/app/advanced-development/modules/container/page.mdx

@@ -56,7 +56,7 @@ import {
 } from "@medusajs/modules-sdk"
 import { Logger } from "@medusajs/medusa"
 
-export default function helloWorldLoader({
+export default async function helloWorldLoader({
   container,
 }: LoaderOptions) {
   const logger: Logger = container.resolve("logger")

www/apps/book/app/advanced-development/modules/options/page.mdx

@@ -90,7 +90,7 @@ type ModuleOptions = {
   capitalize?: boolean
 }
 
-export default function helloWorldLoader({
+export default async function helloWorldLoader({
   options,
 }: LoaderOptions<ModuleOptions>) {
   

www/apps/book/app/basics/loaders/page.mdx

@@ -19,7 +19,7 @@ A loader is created in a TypeScript or JavaScript file under a module's `loaders
 For example, create the file `src/modules/hello/loaders/hello-world.ts` with the following content:
 
 ```ts title="src/modules/hello/loaders/hello-world.ts"
-export default function helloWorldLoader() {
+export default async function helloWorldLoader() {
   console.log(
     "[HELLO MODULE] Just started the Medusa application!"
   )