Get NPM package support working in dogfood

Created by: varungandhi-src

At the moment, we have some NPM packages showing up in the dogfood instance (yay!). However, there is no precise code intelligence for them (surprising...). We need to investigate why referenced NPM packages aren't being auto-indexed and fix that.

One of the blockers for this has been https://github.com/sourcegraph/sourcegraph/issues/30493, but it looks like that should be "fixed" once Eric's patch lands.