AsyncApi 2.2.0: add support for 2.2.0 version of the spec

[char0n]

GitHub release: https://github.com/asyncapi/spec/releases/tag/v2.2.0
Release note: https://deploy-preview-324--asyncapi-website.netlify.app/blog/release-notes-2.2.0

Here is a commit that dealt with AsyncAPI 2.0.0 -> AsyncAPI 2.1.0 migration: c7840c4