message: add missing isDone()
diff: @@ -29,6 +29,10 @@ export class Suspended {
  ) {}
  }
  +export function isDone(s: Status): boolean {
  + return s._tag === "Done"
  +}
  +
  export function withInterrupting(b: boolean) {
  return (s: Status): Status => {
  switch (s._tag) {
  