As [1] revealed, unfiltered loading of unsupported artifacts can impact the
ingestion time for no good reason.

It's not quite reasonable from a resource standpoint, both for the mirror we are
downloading the artifacts and our own infra. So for the time being, we might as
well filter out unsupported artifacts (based on their extension most likely).

The aim is to make that list short and even short-lived (to subside with better
artifacts support).

I recall @lewo should have a fair subset of those unsupported extensions since
he filtered them out of the nix listing ([2] should help)

[1] https://forge.softwareheritage.org/T2485#46361

[2] https://nix-community.github.io/nixpkgs-swh/#by-file-types