Add skeleton for dropdown component

app/Playground/Components/page.tsx

@@ -1,6 +1,7 @@
 "use client";
 
 import Button from "@/components/ui/Button";
+import Dropdown from "@/components/ui/Dropdown";
 import Form from "@/components/ui/Form";
 import NavLink from "@/components/ui/NavLink";
 import RoundedContainer from "@/components/ui/RoundedContainer";
@@ -48,6 +49,11 @@ export default function Components() {
           <p>More Contents</p>
         </div>
       </RoundedContainer>
+
+      <h1>Dropdown</h1>
+      <Dropdown>
+        <p>Hello!</p>
+      </Dropdown>
     </div>
   );
 }