Popsu-coloque/web/themes/custom/popsu_colloque/css/layout.css

/**
 * @file
 * Presentational styles for Drupal stark theme layout.
 *
 * It is left empty for testing purposes.
 *
 * @see https://www.drupal.org/project/drupal/issues/2349711
 */
article img,
.side_notes img{
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.layout-content > div{
  display: flex;
}
.side_notes{
  position: relative;
}

.side_notes > *{
  position: absolute;
}