DIDComm and IPLD integration

[codynhat]

Core functionality of integrating DIDComm Messaging with IPLD.

The interact package should have a simple API that allows sending and handling DIDComm messages.

• Add base message handler that decodes JSON -> DAG-JSON -> IPLD node
• Base handler parses attachments into a CAR
• Waku DIDComm transport that uses DAG-JOSE + DAG-CBOR