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/ComposedModal/ModalFooter.svelte

@@ -1,22 +1,18 @@
 <script>
-  let className = undefined;
-  export { className as class };
   export let primaryClass = undefined;
-  export let primaryButtonText = '';
+  export let primaryButtonText = "";
   export let primaryButtonDisabled = false;
   export let secondaryClass = undefined;
-  export let secondaryButtonText = '';
+  export let secondaryButtonText = "";
   export let danger = false;
-  export let style = undefined;
 
-  import { getContext } from 'svelte';
-  import { cx } from '../../lib';
-  import Button from '../Button';
+  import { getContext } from "svelte";
+  import { Button } from "../Button";
 
-  const { closeModal, submit } = getContext('ComposedModal');
+  const { closeModal, submit } = getContext("ComposedModal");
 </script>
 
-<div class={cx('--modal-footer', className)} {style}>
+<div class:bx--modal-footer={true} {...$$restProps}>
   {#if secondaryButtonText}
     <Button kind="secondary" class={secondaryClass} on:click={closeModal}>
       {secondaryButtonText}
@@ -24,9 +20,9 @@
   {/if}
   {#if primaryButtonText}
     <Button
-      class={primaryClass}
       kind={danger ? 'danger' : 'primary'}
       disabled={primaryButtonDisabled}
+      class={primaryClass}
       on:click={submit}>
       {primaryButtonText}
     </Button>