pinafore/routes/_components/timeline/MoreHeader.html

<div class="more-items-header">
  <button class="primary" type="button" on:click="onClick(event)">
    Show {{count}} more
  </button>
</div>
<style>
  .more-items-header {
    display: flex;
    padding: 5px;
    align-items: center;
    justify-content:center;
  }
</style>
<script>
  export default {
    methods: {
      onClick(event) {
        let onClick = this.get('onClick')
        if (onClick) {
          onClick(event)
        }
      }
    }
  }
</script>