feat: Implement user addition in StubUserManager

src/App.vue

@@ -1,6 +1,6 @@
 <script setup lang="ts">
 import { RouterView } from 'vue-router'
-import { onMounted, onUnmounted, watch, ref } from 'vue';
+import { onMounted, onUnmounted, watch } from 'vue';
 import { useRoute, useRouter } from 'vue-router';
 import { useUserInfo } from "@/composables/useUserInfo";
 import {Dark } from "quasar";