feat(data-table): add ToolbarMenu

Requires menuRef from OverflowMenu to be exported.

src/DataTable/Toolbar.svelte

@@ -4,9 +4,26 @@
    * @type {"sm" | "default"} [size="default"]
    */
   export let size = "default";
+
+  import { setContext } from "svelte";
+
+  let ref = null;
+
+  setContext("Toolbar", {
+    setOverflow: (toggled) => {
+      if (ref) {
+        if (toggled) {
+          ref.style.overflow = "visible";
+        } else {
+          ref.removeAttribute("style");
+        }
+      }
+    },
+  });
 </script>
 
 <section
+  bind:this="{ref}"
   aria-label="data table toolbar"
   class:bx--table-toolbar="{true}"
   class:bx--table-toolbar--small="{size === 'sm'}"