Introduce v3 compatibility tests #247

It's time to update this repository and prepare tests for current versions of AsyncAPI specification

Main goal is to provide properly written set of JSON and YAML documents for each specification component: server, channel, message,security schemas, different variants of injectable schemas like Avro, JSON schemas, XML and so on

This test suite will be used in https://github.com/asyncapi/spec-json-schemas to ensure that new changes are valid across components

Readiness criteria:

1. repository contains all required examples of specification components - valid ones and non valid ones to test JSON Schema constraints
2. tests can be executed trough cli