message: add export to index.d.ts
diff: @@ -472,3 +472,8 @@ declare module '@primer/components/src/Dialog' {
  import {Dialog} from '@primer/components'
  export default Dialog
  }
  +
  +declare module '@primer/components/src/ProgressBar' {
  + import {ProgressBar} from '@primer/components'
  + export default ProgressBar
  +}
  