Provide an ability to create ECS clusters conditionally

[pa-yourserveradmin-com]

It will be fine to have an ability to create ECS clusters conditionally, for example, by using create_ecs variable as this done for terraform-aws-ecs module.

Example of usage:

module "ecs-cluster" {
  # insert the 4 required variables here

  create_ecs = "${terraform.workspace == "default" ? true : false}"

  source  = "azavea/ecs-cluster/aws"
  version = "2.0.0"
}