drupal/core/themes/classy/css/components/pager.css

/**
 * @file
 * Visual styles for pager.
 */

.pager__items {
  clear: both;
  text-align: center;
}
.pager__item {
  display: inline;
  padding: 0.5em;
}
.pager__item.is-active {
  font-weight: bold;
}