Update vue-cli monorepo to v4 (#31)

Author: renovate[bot]

demo/package.json

@@ -15,9 +15,9 @@
   },
   "devDependencies": {
     "@kazupon/vue-i18n-loader": "^0.4.1",
-    "@vue/cli-plugin-babel": "^3.11.0",
-    "@vue/cli-plugin-eslint": "^3.11.0",
-    "@vue/cli-service": "^3.11.0",
+    "@vue/cli-plugin-babel": "^4.0.0",
+    "@vue/cli-plugin-eslint": "^4.0.0",
+    "@vue/cli-service": "^4.0.0",
     "babel-eslint": "^10.0.1",
     "eslint": "^5.16.0",
     "eslint-plugin-vue": "^6.0.0",