Implement a utility useTimeout(callback, delay) that invokes a callback function after a specified delay.

Unlike using plain setTimeout, this utility should be reactive to changes in callback or delay values:

• If the callback changes, the latest callback should be invoked when the timer fires.
• If the delay changes, any pending timer should be canceled and a new one scheduled.
• If delay is null, the timeout should be cleared and the callback never runs.

Your task: Implement useTimeout(callback, delay) so that:

• It automatically cleans up when canceled.
• It always calls the most recent callback.

Example

let loading = true;

useTimeout(() => {
  loading = false;
}, 1000);

// Initially: loading = true
// After 1000ms → loading = false

This mimics React’s useTimeout pattern but can be used in plain JavaScript too.