Convert SuperSelect::Placeholder to TypeScript

Author: alex-ju

packages/components/src/components/hds/form/super-select/placeholder.hbs

@@ -1,4 +1,3 @@
-{{! @glint-nocheck: not typesafe yet }}
 {{!
   Copyright (c) HashiCorp, Inc.
   SPDX-License-Identifier: MPL-2.0

packages/components/src/components/hds/form/super-select/placeholder.ts

@@ -0,0 +1,12 @@
+import templateOnlyComponent from '@ember/component/template-only';
+
+interface HdsFormSuperSelectPlaceholderSignature {
+  Args: {
+    placeholder?: string;
+  };
+}
+
+const HdsFormSuperSelectPlaceholderComponent =
+  templateOnlyComponent<HdsFormSuperSelectPlaceholderSignature>();
+
+export default HdsFormSuperSelectPlaceholderComponent;