[MLS] New Go implementation of RFC 9420

[Ian Chechin <[e-mail]>]

Hello MLS WG,

I have been working on a pure-Go implementation of RFC 9420 and wanted to
introduce it to the working group:
https://github.com/Deln0r/mls-go

Current scope is the MTI ciphersuite
(MLS_128_DHKEMX25519_AES128GCM_SHA256_Ed25519): TLS presentation language
codec, the crypto primitives (HKDF, AES-128-GCM, Ed25519, HPKE base mode
over DHKEM(X25519, HKDF-SHA-256)), array-based ratchet tree with the full
math layer, and the section 8.1 key schedule. A 3-member group flow
(creator + two joiners via Welcome) is exercised end-to-end by a CI smoke
test.

I have looked at thomas-vilte/mls-go (partial) but have not found other
active Go impls. Curious whether the WG knows of any in-progress work I
should be coordinating with, and what the preferred channel is for
reporting mls-implementations test vector conformance once I get to that
point.

Happy to share design notes or take review on specific subpackages.

Regards,
Ian Chechin