refactor: use $$restProps API

- add ref prop for applicable components (#196)
- add slot to Content Switcher `Switch` component (#183)
- remove fillArray, css utilities

src/components/ContentSwitcher/ContentSwitcher.Story.svelte

@@ -1,11 +1,13 @@
 <script>
   export let story = undefined;
 
-  import Layout from '../../internal/ui/Layout.svelte';
-  import ContentSwitcher from './ContentSwitcher.svelte';
-  import Switch from './Switch.svelte';
+  import Layout from "../../internal/ui/Layout.svelte";
+  import ContentSwitcher from "./ContentSwitcher.svelte";
+  import Switch from "./Switch.svelte";
+  import Add16 from "carbon-icons-svelte/lib/Add16";
 
-  let selectedIndex = 0;
+  $: selectedIndex = 0;
+  $: console.log("bind selectedIndex", selectedIndex);
 </script>
 
 <Layout>
@@ -26,7 +28,19 @@
       }}>
       <Switch {...$$props} text="First section" />
       <Switch {...$$props} text="Second section" />
-      <Switch {...$$props} text="Third section" />
+      <Switch {...$$props}>
+        <div style="display: flex; align-items:center;">
+          <Add16 style="margin-right: .25rem;" />
+          Third section
+        </div>
+      </Switch>
     </ContentSwitcher>
+    <div
+      style="margin-top: 1.5rem"
+      on:click={() => {
+        selectedIndex = 1;
+      }}>
+      Programmatically set to second index
+    </div>
   {/if}
 </Layout>