Add optional web3 storage upload

[bmann]

Summary

Web3 Storage has moved to a new UCAN-based API.

Problem

Use Fission for app and DNS infra, use web3 storage for persistence.

Solution

Skip spinning up a Kubo node, upload to web3 storage (key materials in ENV?), and then when the content-address of the upload is returned, only change the DNSLink of the Fission app.

Challenge: Fission gateway will only serve Fission-uploaded content. Can we allow list w3s? Or, recommend other gateway provider, at which point we're only using the DNS update, and this could be much simpler without this action.