/**
 * Shared IntersectionObserver instance. Simple wrapper around the native API.
 */
/**
 * Observe an element for intersection with the viewport. Call the passed callback when the intersection changes.
 * @param {Element} el - Element to observe
 * @param {ObserverCallback} callback - Callback to call when the intersection changes
 * @returns {() => void} Unobserve function
 */
export declare function observe(el: HTMLElement, callback: (isIntersecting: boolean) => void): () => void;