Can we deploy this with npm?

[blasscoc]

Would it be possible to make it so we can npm install this app?

There's nothing wrong yarn, many svelte apps on the REPL are available with npm, and getting yarn adds an extra step.

[unbiased-dev]

Npm and Yarn are interoperable. You can just npm i @sveltejs/svelte-virtual-list. You don't need yarn.