main.tsでimport App from '@/App.vueがエラーになるのを修正

vuejs/vue-cli#1198 (comment)

Author: xmitoux

src/vue-shim.d.ts

@@ -0,0 +1,5 @@
+declare module '*.vue' {
+    import { defineComponent } from 'vue';
+    const component: ReturnType<typeof defineComponent>;
+    export default component;
+}