function getContentRect(el) {
	let rect = getRect(el);
	const paddingLeft = parseInt(css(el, 'padding-left')),
		paddingTop = parseInt(css(el, 'padding-top')),
		paddingRight = parseInt(css(el, 'padding-right')),
		paddingBottom = parseInt(css(el, 'padding-bottom'));
	rect.top += paddingTop + parseInt(css(el, 'border-top-width'));
	rect.left += paddingLeft + parseInt(css(el, 'border-left-width'));
	// Client Width/Height includes padding only
	rect.width = el.clientWidth - paddingLeft - paddingRight;
	rect.height = el.clientHeight - paddingTop - paddingBottom;
	rect.bottom = rect.top + rect.height;
	rect.right = rect.left + rect.width;
	return rect;
}
Returns the content rect of the element (bounding rect minus border and padding)
@param {HTMLElement} el