Implement a debounce function

## Problem: Implement `debounce(fn, wait)` Implement a `debounce` utility function. ### Behavior Given a function `fn` and a delay `wait` (milliseconds), `debounce(fn, wait)` returns a new function `debounced` such that: - When `debounced(...args)` is called repeatedly, it postpones calling `fn` until **after** `wait` ms have elapsed since the **most recent** call. - When the timer finally expires, `fn` is invoked **once** with the **latest** arguments and the original `this` context. ### Requirements - Preserve `this` binding when invoking `fn`. - The returned function should be callable multiple times. ### Optional extensions (if time) - Support `debounced.cancel()` to cancel a pending invocation. - Support `debounced.flush()` to immediately run the pending invocation (if any).