function showNotification(container, message) {
    const element = createElement('div', {
        className: 'notification',
        innerHTML: message
    }, container);

    setTimeout(() => {
        element.style.opacity = 0;
    }, 1000);
    setTimeout(() => {
        container.removeChild(element);
    }, 2000);
}
Shows notification message.
@param {Node} container - Node in which the notification panel is shown
@param {string} message - Notification message