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/Accordion/Accordion.svelte

@@ -1,28 +1,21 @@
 <script>
-  let className = undefined;
-  export { className as class };
-  export let style = undefined;
-
+  export let align = "end"; // "start" | "end"
   export let skeleton = false;
-  export let count = 4;
-  export let open = true;
 
-  import { cx } from '../../lib';
-  import AccordionSkeleton from './Accordion.Skeleton.svelte';
+  import AccordionSkeleton from "./Accordion.Skeleton.svelte";
 </script>
 
 {#if skeleton}
-  <AccordionSkeleton {count} {open} class={className} {style} />
-{/if}
-
-{#if !skeleton}
+  <AccordionSkeleton {...$$restProps} />
+{:else}
   <ul
+    class:bx--accordion={true}
+    class="bx--accordion--{align}"
+    {...$$restProps}
     on:click
     on:mouseover
     on:mouseenter
-    on:mouseleave
-    class={cx('--accordion', className)}
-    {style}>
+    on:mouseleave>
     <slot />
   </ul>
 {/if}