Create KT for lookup table sourced from Mysql/Postgres connector

This was first brought up in https://github.com/confluentinc/kafka-tutorials/pull/649 during a "Stream Processing Recipe" migration of the recipe "Lookups". @bbejeck suggested to speak to using a connector to create a lookup table in the join-streams-table KT and to also...
>... have a separate tutorial to do just that; the user runs Mysql/Postgres in docker, and part of the tutorial flow is to setup up Kafka connect to pull the data. While this type of tutorial would have a good amount of overlap, we could make the Kafka Connect pulling from the database for live updates the tutorial's main feature.

This issue is to create the tutorial described above.