message: Update ProgressBox to use Freestyle::Usage
diff: import Component from '@glimmer/component';
  +import { tracked } from '@glimmer/tracking';
  -const sampleMilestones = [
  +const SAMPLE_MILESTONS = [
  {
  title: 'Place order',
  statusOnCompletion: 'Order placed',
  @@ -20,5 +21,9 @@ const sampleMilestones = [
  ];
  export default class ProgressBoxUsageComponent extends Component {
  - sampleMilestones = sampleMilestones;
  + milestones = SAMPLE_MILESTONS;
  + @tracked title = "Customer Support";
  + @tracked status = "Products reserved";
  + @tracked size = 120;
  + @tracked completedCount = 2;
  }
  