chieve this type of layout,
you can specify the number of columns the item should expand to by setting the custom property
`--app-grid-expandible-item-columns`. To indicate which item should expand, apply the mixin
`--app-grid-expandible-item` to a rule with a selector to the item. For example:

<pre><code>
&lt;template>
  &lt;style include="app-grid-style">
    :host {
      --app-grid-columns: 3;
      --app-grid-item-height: 100px;
      --app-grid-expandible-item-columns: 3;
    }

    /* Only the first