new multi-sig DID method to support multi-writer streams

[qbig]

<REMOVE>--- cip: title: DID Mult Methods author: Liang Qiao (@qbig ), Spencer T Brody(@stbrody) discussions-to: https://forum.ceramic.network/t/is-it-possible-to-create-streams-controlled-by-multiple-did/746/9 status: <Idea> category: <Standards> type: <RFC> created: 2023-02-21 requires: <EIP number(s)> replaces: <EIP number(s)> <REMOVE>---

Simple Summary

Simple summary goes here.

Abstract

Abstract goes here.

Motivation

Motivation goes here.

Specification

Specification goes here.

Rationale

Rationale goes here.

Backwards Compatibility

Backwards compatibility goes here.

Implementation

Implementation goes here.

Security Considerations

Security considerations go here.

Copyright

Copyright and related rights waived via CC0.

[qbig]

https://github.com/ceramicnetwork/CIP/pull/122