footer {
    background:  rgb(21, 208, 255);
    margin: auto;
    border-radius: 0 0 20px 20px;
    color: #fff;
    text-align: center;
    padding: 30px;
    box-sizing: border-box;
    font-size: 18px;

}
.libro{
    display: flex;
    justify-content: center;
    text-align: center;
}