updated App.vue to use new <script setup lang="ts"> syntax

src/App.vue

@@ -14,40 +14,33 @@
   <CookieConsentBtn id="cookie-btn" />
 </template>
 
-<script>
-import Nav from "/src/components/NavComponent.vue";
-import Footer from "/src/components/FooterComponent.vue";
-import CookieConsentBtn from "/src/components/CookieConsentBtn.vue";
+<script setup lang="ts">
+import Nav from "@/components/NavComponent.vue";
+import Footer from "@/components/FooterComponent.vue";
+import CookieConsentBtn from "@/components/CookieConsentBtn.vue";
 import { onMounted, ref } from "vue";
-import InfoModal from "/src/components/InfoModal.vue";
+import InfoModal from "@/components/InfoModal.vue";
 
-export default {
-  components: { InfoModal, Footer, Nav, CookieConsentBtn },
-  setup() {
-    const offset = ref(0);
+const offset = ref(0);
 
-    const setOffset = () => {
-      return document.getElementsByTagName("nav")[0].clientHeight;
-    };
-
-    const setBgHeight = () => {
-      document.querySelector(".bg-img").style.height =
-        document.documentElement.clientHeight + "px";
-    };
-
-    window.onresize = () => {
-      offset.value = setOffset();
-      setBgHeight();
-    };
-
-    onMounted(() => {
-      offset.value = setOffset();
-      setBgHeight();
-    });
-
-    return { offset };
-  },
+const setOffset = () => {
+  return document.getElementsByTagName("nav")[0].clientHeight;
 };
+
+const setBgHeight = () => {
+  const bgImg = document.querySelector(".bg-img") as HTMLImageElement;
+  bgImg.style.height = document.documentElement.clientHeight + "px" || "0px";
+};
+
+window.onresize = () => {
+  offset.value = setOffset();
+  setBgHeight();
+};
+
+onMounted(() => {
+  offset.value = setOffset();
+  setBgHeight();
+});
 </script>
 
 <style lang="scss">