Properly configure ECMAScript version of frontend

frontend/package.json

@@ -27,6 +27,7 @@
     "@vue/tsconfig": "^0.5.1",
     "eslint": "^9.14.0",
     "eslint-plugin-vue": "^9.30.0",
+    "msw": "^2.7.0",
     "npm-run-all2": "^7.0.1",
     "sass": "1.77.8",
     "sass-embedded": "^1.77.8",
@@ -37,7 +38,8 @@
     "vite": "^5.4.10",
     "vite-plugin-vuetify": "^2.0.3",
     "vue-router": "^4.4.0",
-    "vue-tsc": "^2.1.10"
+    "vue-tsc": "^2.2.0",
+    "@vue/language-server": "^2.2.0"
   },
   "engines": {
     "node": "^20.16",