Add support for CACAO -> UCAN delegation

[Chain-agnostic Capability Objects (CACAOs)](https://github.com/ChainAgnostic/CAIPs/blob/master/CAIPs/caip-74.md) are a way to encapsulate Sign-in with Everything (e.g., Ethereum, Solana etc.) delegations from a did:pkh to any DID. To achieve seamless UX with existing Blockchain wallets (e.g. Ethereum), it is critical to add support for CACAO Delegations in capability chains. This would enable users with existing Blockchain wallets to use their Blockchain wallet to get access to their DWN.