function isElementOffDocument(el) {
    const rect = getAbsoluteRect(el);
    return rect.right < 0 || rect.left > document.documentElement.scrollWidth || rect.bottom < 0 || rect.top > document.documentElement.scrollHeight;
}
@param {HTMLElement} el - the element to check
@returns {boolean} - true if the element in its entirety is off-screen including the scrollable area (the normal dom events look at the mouse rather than the element)