Add `npm list --json` to /admin

* Tack on a virtual model name since we have no control over this implied native DB model.

Applies to #296 

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This appears to be the only way it can be done for listing the current dependencies. I haven't found any native API to Node.js that does this... so I'm willing to give this a whirl.

@Zren and @OpenUserJs/owners any objections?