How do I set up type inference in $app/stores for data returned in +page.js?

[theetrain]

I understand there's a generated $types file that can be consumed in +page.js in order to apply typings to my loader. Given the following:

+page.js

export const prerender = true

/** @type {import('./$types').PageLoad} */
export function load () {
  return {
    meta: { // custom output
      title: 'This is my meta title'
    }
  }
}

+layout.svelte

<script>
  import { page } from '$app/stores';
</script>

<!-- ⚠️ No auto-completion -->
<p>{$page.data.meta.title}</p>

<slot />

How do I apply type inference so that $page.data.meta.title can show me its type and auto-completion in +layout.svelte?

Related docs:

• Loading data
• Types: Load

Probably relates to #647