ci: adds Dockerfile and modifies github actions workflow

I'll approve. It's not entirely clear how the environment variables set in ECS are transferred in the container. You might need an additional step to do that in the Dockerfile unless you've already tested for that.

The environment variables will be set in terraform (in the task definition resource). Every time an ECS task is run, the container running the task will get those variables from the task definition.

AllenNeuralDynamics / aind-data-asset-indexer

ci: adds Dockerfile and modifies github actions workflow #28