feat(components): add Tile

Supports #34

TODO:

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

src/components/Tile/RadioTile.svelte

@@ -0,0 +1,59 @@
+<script>
+  // TODO: compose as "children" components
+  let className = undefined;
+  export { className as class };
+  export let checked = false;
+  export let id = Math.random();
+  export let name = '';
+  export let iconDescription = 'Tile checkmark';
+  export let value = '';
+  export let tabIndex = 0;
+  export let light = false;
+  export let props = {};
+
+  import { createEventDispatcher } from 'svelte';
+  import CheckmarkFilled16 from 'carbon-icons-svelte/lib/CheckmarkFilled16';
+  import { cx } from '../../lib';
+
+  const dispatch = createEventDispatcher();
+
+  function handleChange(event) {
+    dispatch('change', event);
+  }
+
+  function handleKeyDown(event) {
+    if (event.key === ' ' || event.key === 'Enter') {
+      event.preventDefault();
+      handleChange(event);
+    }
+
+    dispatch('keydown', event);
+  }
+
+  $: _class = cx(
+    '--tile',
+    '--tile--selectable',
+    checked && '--tile--is-selected',
+    light && '--tile--light',
+    className
+  );
+</script>
+
+<input
+  {...props}
+  type="radio"
+  class={cx('--tile-input')}
+  on:change
+  on:change={handleChange}
+  {id}
+  {name}
+  {value}
+  {checked} />
+<label for={id} class={_class} tabindex={tabIndex} on:keydown={handleKeyDown}>
+  <span class={cx('--tile__checkmark')}>
+    <CheckmarkFilled16 aria-label={iconDescription} title={iconDescription} />
+  </span>
+  <span class={cx('--tile-content')}>
+    <slot />
+  </span>
+</label>