Function resizeObservable

resizeObservable(
elem: Readonly<Element>,
interval?: Interval,
): Reactive<ResizeObserverEntry[]>
Observe when element resizes. Specify interval to debounce, uses 100ms by default.
```
const o = resizeObservable(myEl, 500);
o.subscribe(() => {
 // called 500ms after last resize
});
```
Parameters
- elem: Readonly<Element>
- Optionalinterval: Interval
  Tiemout before event gets triggered
Returns Reactive<ResizeObserverEntry[]>