title: custom hook not updating components
body: <p>I wrote a simple custom hook to control a countdown timer. In it, I have a state variable for the remaining seconds. Subtraction from this variable is triggered on a button click, and should subtract 1000 ms per second of interval. The Display component is responsible for showing the changed <code>seconds</code> variable</p>
  <p>The functions get triggered appropriately, aka the subtraction is working internally, however, the change in seconds is not propagated to all components and the display component does not change. See <a href="https://codesandbox.io/s/bold-wu-j6ti3" rel="nofollow noreferrer">CodeSandBox</a>.</p>
  <p>I was under the impression that the change in state (seconds) should also re-render its dependent recipients since the seconds variable is used there.</p>
  <p>How do I get the Display component to track the change in value?</p>