Untitled

<!DOCTYPE html>
<html>
<head>
<title>Usuários</title>
<meta charset="UTF-8">
<script src="https://cdn.jsdelivr.net/npm/vue"></script>
</head>
<body>

<div id="app">
  <input v-model="newUser">
  <button v-on:click="addUser">Add</button>

  <ol>
    <li v-for="user in users">
      {{ user.name }}
    </li>
  </ol>
</div>

<script>
var app = new Vue({
  el: '#app',
  data: {
    newUser: '',
    users: [
      { name: 'João' },
      { name: 'Pedro' },
      { name: 'Guilherme' }
    ]
  },
  methods: {
    addUser: function () {
      if(this.newUser) {
        this.users.push({name: this.newUser})
      }
    }
  }
})
</script>

</body>
</html>