Update tutorial from `use:` to `@attach`

[hyunbinseo]

Existing tutorial is based on the use: directive.

https://svelte.dev/tutorial/svelte/actions

<div class="menu" use:trapFocus>

This should be updated to @attach:

https://svelte.dev/docs/svelte/use

In Svelte 5.29 and newer, consider using attachments instead, as they are more flexible and composable.