feat(components): add Tile

Supports #34

TODO:

- remove exported props
- compose TileGroup, SelectableTile, RadioTile components

src/components/Tile/ClickableTile.svelte

@@ -0,0 +1,42 @@
+<script>
+  let className = undefined;
+  export { className as class };
+  export let href = undefined;
+  export let rel = undefined;
+  export let light = false;
+  export let clicked = false;
+  export let props = {};
+
+  import { createEventDispatcher, tick } from 'svelte';
+  import { cx } from '../../lib';
+
+  const dispatch = createEventDispatcher();
+
+  async function handleClick(event) {
+    clicked = !clicked;
+    await tick();
+    dispatch('click', event);
+  }
+
+  async function handleKeyDown(event) {
+    if (event.key === ' ' || event.key === 'Enter') {
+      clicked = !clicked;
+      await tick();
+    }
+
+    dispatch('keydown', event);
+  }
+
+  $: _class = cx(
+    '--link',
+    '--tile',
+    '--tile--clickable',
+    clicked && '--tile--is-clicked',
+    light && '--tile--light',
+    className
+  );
+</script>
+
+<a {...props} class={_class} on:click={handleClick} on:keydown={handleKeyDown} {href} {rel}>
+  <slot />
+</a>