Add siblingContainers and dependsOn options to the task definitions

[swiknaba]

Usage example where a 2nd process is launched within each task that runs Rails; in this example, the open telemetry collector for AWS XRay.

Patched that in as alpha-1 to the 0.8.x release, let me know if any other version should be used for that.

# ecsx.yml

tasks:
  $rails: &rails
    <<: *default
    envVars:
      PORT: "3000"
      RAILS_MAX_THREADS: "4"
    secrets:
      - name: app
        keys:
          - RAILS_MASTER_KEY
          - DATABASE_URL_MASTER
  aws_otel_collector:
    image: "amazon/aws-otel-collector:v0.20.0"
    command:
      - --config=/etc/ecs/ecs-default-config.yaml


  web:
    <<: *rails
    command:
      - bundle
      - exec
      - puma
    siblingContainers:
      - aws_otel_collector
    dependsOn:
      - containerName: "aws_otel_collector"
        condition: "START"

[marcqualie]

@swiknaba @samkahchiin Thanks for the contribution! 🎉