docs: Add docs for running dbt core in airflow via cosmos

[chrishronek]

Summary

I noticed that you have a lot of dbt adapters as part of your base image, if you advised customers to follow this guide, you could avoid the pain of maintaining those.

Test Plan

I've successfully deployed this to a plural.sh Airflow instance to confirm that it works.

Checklist

• No images hosted from dockerhub
• Are dashboards present to understand the health of the application. There must be at least 1 of these
  • all databases should have dashboards
  • ideally also have at least cpu/mem utilization dashboards for webserver tier of the app
  • you can use plural from-grafana to convert a grafana dashboard found via google to our CRD
• Are scaling runbooks present
  • all databases must have scaling runbooks
  • you can use the charts in pluralsh/module-library to accelerate this
• do you need to add config overlays?
  • inputing secrets
  • configuring autoscaling
• If there’s a web-facing component to the app, we need to support OIDC authentication and setting up private networks if no authentication option is viable
• All major clouds must be supported
  • Azure
  • AWS
  • GCP

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Again, not sure if any of the above were really applicable since this is just a doc, but let me know if you'd like me to change anything!

[michaeljguarino]

could we drop the png? I don't know if the markdown renderer will handle that properly actually.