Start dev for deno:
deno task dev
Build:
deno task build
And then serve using Deno, as per https://github.com/pluvial/svelte-adapter-deno :
deno run --allow-env --allow-read --allow-net build/index.js
Adding an npm (dev) dependency, here sass-embedded
as an example (updates package.json and deno.lock):
deno add -D npm:sass-embedded