Add a reference deployment for ECS

Summary:
This demonstrates how to use docker-compose do deploy a Dagster stack to
ECS (and how to run the same stack locally for development). I chose the
docker-compose route over with several different alternatives
(CloudFormation template, AWS Copilot, Terraform, etc.):

• CloudFormation and Terraform force our hand toward taking on too much devops responsibility (providing recommendation on how to setting up VPCs, Load Balancers, etc.)
• Copilot's tooling wasn't mature enough
• Several users have recently expressed interest in trying to deploy our

deploy_docker docker-compose.yaml to ECS.

Test Plan:
I'm mainly putting this up for comments right now but if we like the
direction it's heading, we could mimic the type of tests run in our
deploy_docker example.

Reviewers: johann, dgibson, catherinewu

Reviewed By: dgibson

Subscribers: alangenfeld

Differential Revision: https://dagster.phacility.com/D8292