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/Breadcrumb/Breadcrumb.svelte

@@ -1,21 +1,17 @@
 <script>
-  let className = undefined;
-  export { className as class };
   export let noTrailingSlash = false;
-  export let style = undefined;
-
-  import { cx } from '../../lib';
 </script>
 
 <nav
+  aria-label="Breadcrumb"
+  {...$$restProps}
   on:click
   on:mouseover
   on:mouseenter
-  on:mouseleave
-  aria-label={$$props['aria-label'] || 'Breadcrumb'}
-  class={className}
-  {style}>
-  <ol class={cx('--breadcrumb', noTrailingSlash && '--breadcrumb--no-trailing-slash')}>
+  on:mouseleave>
+  <ol
+    class:bx--breadcrumb={true}
+    class:bx--breadcrumb--no-trailing-slash={noTrailingSlash}>
     <slot />
   </ol>
 </nav>