w3s.link: support application/vnd.ipld.raw

[lidel]

Users should be able to fetch a raw block by explicitly requesting it via ?format=raw or Accept: application/vnd.ipld.raw

Ref.

• https://www.iana.org/assignments/media-types/application/vnd.ipld.raw
• https://docs.ipfs.tech/reference/http/gateway/#example-fetching-a-single-raw-block-from-a-public-gateway