[Svelte] Attach components to classes/objects for use in template

App.svelte

<script>
	import Menu from "./Menu"
</script>

<Menu>
	<!-- the Items component on the Menu component's (class) Items property -->
	<Menu.Items />
</Menu>

Items.svelte

Hello world!

Menu.js

import Menu from './Menu.svelte'
import Items from './Items.svelte'

// Svelte components can be imported into plain JavaScript files.
// Svelte components are just JS classes. 
Menu.Items = Items // Since classes have an object portion, you can attach other component references as property values!

export default Menu

Menu.svelte

<slot />