This branch contains 2 new RFCs:
1. An RFC describing the secure 1-to-1 communication channels;
2. An RFC describing the MLS and the decentralized MLS.
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Co-authored-by: Ekaterina Broslavskaya <seemenkina@gmail.com>
Co-authored-by: kaiserd <1684595+kaiserd@users.noreply.github.com>
