gossipsub v1.1 specification

[vyzo]

Specification for the changes in gossipsub v1.1. Implementation:

• https://github.com/libp2p/go-libp2p-pubsub/pull/234
• https://github.com/libp2p/go-libp2p-pubsub/pull/263

[schomatis]

This is a very detailed and well-written document that makes reviewing the implementation changes much easier, thanks @vyzo!

[daviddias]

Note for the reviewers

There are are 4 documents in this spec:

• gossipsub-v1.0.md - The spec of the v1.0 of the gossipsub protocol. This is the doc that implements have to start with
• gossippsub-v1.0-old.md - This was the original spec. It packs a friendly language that is easy to parse.
• gossipsub-v1.1.md - This is the document you should be reviewing!
• episub.md: a research note on a protocol building on top of gossipsub to implement epidemic broadcast trees. You do not need to review this one