Svelte+SSG+Firebase

$ npm i -D @sveltejs/adapter-static@next

import preprocess from 'svelte-preprocess';
import adapter from '@sveltejs/adapter-static';

/** @type {import('@sveltejs/kit').Config} */
const config = {
	preprocess: [
		preprocess({
			postcss: true
		}),
	],
	kit: {
		adapter: adapter({
			pages: 'public',
			assets: 'public'
		}),
		// hydrate the <div id="svelte"> element in src/app.html
		target: '#svelte'
	}
};

export default config;

...
      "build": "npx rimraf public && svelte-kit build",
      "deploy": "npx firebase deploy --only hosting"
...

$ npm run build
...
$ npm run deploy
...