message: add comment linking to PR
diff: @@ -12,6 +12,10 @@ function useForceUpdate() {
  return useMemo(() => () => isMounted.current && setEpoch(x => x + 1), [])
  }
  +/**
  + * For rationale on why this exists
  + * https://github.com/artsy/emission/pull/1900
  + */
  export class GlobalState<T> {
  private listeners: Array<() => void> = []
  constructor(private _current: T) {}
  