feature: Add scheduled ECS task support

[jpelgrims]

Example:

  - id: my-task-family # in case of ECS scheduled tasks, this is the ECS task definition family name
    type: ecs-scheduled-task
    rule: my-eventbridge-rule # the EventBridge rule that schedules this task
    version: v1
    event-bus-name: default # optional, defaults to "default"
    version-environment-key: VERSION # optional, updates the given environment variable in the container with the version when deploying