Converted App.vue to composition api

frontend/src/App.vue

@@ -4,10 +4,10 @@
   </div>
 </template>
 
-<script lang="ts">
-export default {
-  name: "app",
-  mounted() {
+<script setup lang="ts">
+import { onMounted } from 'vue';
+
+onMounted(() => {
   const loading = document.getElementById("loading");
   if(loading !== null) {
     loading.classList.add("done");
@@ -18,6 +18,6 @@ export default {
       }
     }, 200);
   } 
-  },
-};
+})
+
 </script>