SvelteKit: how do I do slug-based dynamic routing?

Question

As of SvelteKit 1.0 the path should be a directory in brackets, e.g. for /blog/<slug> you will add the following:

src/routes/blog/[slug]
  |_ +page.js
  |_ +page.svelte

Then in src/routes/blog/[slug]/+page.js you can add something like

export const load = ({ params }) => {
    return {
        slug: params.slug
    }
}

which will return it as a data property to +page.svelte, so you can write something like:

<script>
    export let data;
</script>

<h1>{data.slug}</h1>

Reference: https://kit.svelte.dev/docs/routing