Preparing the Application (ok)

C:\xampp\htdocs\html\src\main.js

// The Vue build version to load with the `import` command
// (runtime-only or standalone) has been set in webpack.base.conf with an alias.
import Vue from 'vue';
import App from './App';
Vue.config.productionTip = false;
/* eslint-disable no-new */
new Vue({
  el: '#app',
  components: { App },
  template: '<App/>'
})

C:\xampp\htdocs\html\src\App.vue

<template>
  <h1>{{ title }}</h1>
</template>
<script>
export default {
  data() {
    return {
      title: 'My To Do App'
    }
  }
}
</script>