Use _config.yml files, just like Jekyll. Import them inside your script tags and use them as you wish.

_config.yml

title: "Svekyll: blogging with the simplicity and tradition of Jekyll, the futuristic power of Svelte"
theme: cyberpunk

analytics:
  provider: matomo
  matomo:
    site_id: 3
    url: "//a.p.public.do"

Then, use it inside your templates:

<script>
import { config } from '$lib/config';

console.log('Config', config.title);

</script>

<h1>{ config.title }</h1>

You can also use _config.toml files if you prefer TOML