Add basic CI tests

Update postgres version

Change name to new recommended compose.yaml

Change name of dagit service to dagster-webserver in compose

Fix dockerfile after dagit->dagster-webserver rename

Update to latest dagster version

Clean up ruff configuration

Remove black config from pyproject.toml

Update test dependencies

Format tests with ruff instead of black

Update ruff and remove black formatter

Update gitignore

Add .dagster to .gitignore

Update README.md

Change to new Definition api instead of repository