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/Select/SelectItem.svelte

@@ -1,24 +1,31 @@
 <script>
-  let className = undefined;
-  export { className as class };
   export let disabled = false;
   export let hidden = false;
-  export let style = undefined;
-  export let text = '';
-  export let value = '';
+  export let text = "";
+  export let value = "";
 
-  import { getContext } from 'svelte';
-  import { cx } from '../../lib';
+  import { getContext, onDestroy } from "svelte";
 
-  const ctx = getContext('Select') || getContext('TimePickerSelect');
+  const ctx = getContext("Select") || getContext("TimePickerSelect");
 
   let selected = false;
 
-  ctx.selectedValue.subscribe(currentValue => {
-    selected = currentValue === value;
+  const unsubscribe = ctx.selectedValue.subscribe($ => {
+    selected = $ === value;
+  });
+
+  onDestroy(() => {
+    unsubscribe();
   });
 </script>
 
-<option class={cx('--select-option', className)} {value} {disabled} {hidden} {style} {selected}>
+<option
+  {value}
+  {disabled}
+  {hidden}
+  {selected}
+  class:bx--select-option={true}
+  class={$$restProps.class}
+  style={$$restProps.style}>
   {text || value}
 </option>