[MyMeta] Migrate the web3.storage proxy from Express to Next.js

[dysbulic]

web3.storage authenticates using an API key. That key can't be inserted into the React app or users would be able to delete each other's files.

To protect the key, a proxy is used where the user sends to the proxy and the proxy uploads to web3.storage returning the CIDs of where the files are stored.

@Cali93 & I put the proxy code in the Express server just to get it working. That Express server is deployed to a private subnet only accessible to Hasura in production, so it can't be used as the proxy.

It should be possible to migrate the proxy code to a Next.js API endpoint. web3.storage requires Webpack 5 (and MyMeta is on 4 currently), but it oughtn't be used for the API endpoints.

[dysbulic]

A Next.js API endpoint fronting web3.storage is part of Ceramic's NFT Example: https://github.com/ceramicstudio/dynamic-nft-example/blob/main/pages/api/persist.ts