Tutorial: produce/consume schema messages using console tools

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Produce/consume messages in avro, protobuf, and json schema formats using just console tools // cc @dlfaraujo

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For Avro: https://docs.google.com/document/d/1rP9AMQfHZRZNzhTK0FaFvBa3H7LoZdP_j7EvVaWuwic/

[dlfaraujo]

For Protobuf: https://docs.google.com/document/d/1vnfCTnlBNO9RwZvAjEIqsgEP6TYl2KAiD_vprMnzc1Q/

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For JSON Schema: https://docs.google.com/document/d/1wOCzVNSSq5VM0GMRs4cE4y0X5MH8blfai8hkw09bLPY/

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WIP branch for Avro is https://github.com/confluentinc/kafka-tutorials/tree/feature/console-tools-1-490