feat(components): add StructuredList

Closes #27

src/components/StructuredList/StructuredListWrapper.svelte

@@ -0,0 +1,45 @@
+<script>
+  let className = undefined;
+  export { className as class };
+  export let defaultSelected = undefined;
+  export let border = false;
+  export let selection = false;
+  export let style = undefined;
+
+  import { createEventDispatcher, setContext } from 'svelte';
+  import { writable } from 'svelte/store';
+  import { cx } from '../../lib';
+
+  const dispatch = createEventDispatcher();
+  const _class = cx(
+    '--structured-list',
+    border && '--structured-list--border',
+    selection && '--structured-list--selection',
+    className
+  );
+
+  let selected = writable(defaultSelected);
+
+  setContext('StructuredListWrapper', {
+    selected,
+    update: value => {
+      selected.set(value);
+    }
+  });
+
+  $: {
+    defaultSelected = $selected;
+    dispatch('change', $selected);
+  }
+</script>
+
+<section
+  on:click
+  on:mouseover
+  on:mouseenter
+  on:mouseleave
+  class={_class}
+  aria-label={$$props['aria-label'] || 'Structured list section'}
+  {style}>
+  <slot />
+</section>