EIP-4844: Shard Blob Transactions

[etan-status]

Made a concrete proposal for eth/68 changes here:

• EIP-5793: eth/68 Add transaction type to tx announcement - #2 by etan-status

For SSZ Optional, opened a PR:

• Update EIP-4844: Use SSZ `Optional` for `Address` by etan-status · Pull Request #6495 · ethereum/EIPs · GitHub