How to get IPLD Car file

[tennox]

Kinda figured out how to use this - see #14 (comment)

but I need to fetch car files for dag-json encoded IPLD data, which I half-figured out:

I needed to modify sw-core to use r.searchParams.set("dag-scope", "all") (was: entity).
The request to saturn.ms returns the car file correctly, but the service worker response returns a network error trying to read the response 😞:

TypeError: Failed to fetch

see this branch on the demo repo & the deployed demo (check console)