Create basic loading screen

client/src/components/Loading.tsx

+import { Spinner } from "react-bootstrap";
+
+function Loading() {
+  return (
+    <div className="vh-100 vw-100 d-flex justify-content-center align-items-center">
+      <Spinner animation="border" />
+    </div>
+  );
+}
+
+export default Loading;