css: misc changes - anchor links in list elements can now be displayed more obviously using "list__item--show-links" class - specific style for disabled button - adapted form styles to new "select" field - other small changes, see diff

#body {
    display: flex;
    align-items: center;
    justify-content: center;
}

#link_section {
    font-weight: bold;
    text-align: center;
    font-size: 1.5rem;
}

article p:last-child {
    text-align: center;
}