Mention `defineModel()` for Vue 3

[ShayanTheNerd]

In "emit to parent" feature for Vue 3, the code can be simplified to the following:

App.vue

<script setup>
import { ref } from "vue";

import AnswerButton from "./AnswerButton.vue";

const isHappy = ref(true);
</script>

<template>
  <p>Are you happy?</p>

  <AnswerButton v-model="isHappy" />
  
  <p style="font-size: 50px">
    {{ isHappy ? "😀" : "😥" }}
  </p>
</template>

AnswerButton.vue

<script setup>
const isHappyModel = defineModel({ type: Boolean });
</script>

<template>
  <button @click="isHappyModel = true">YES</button>
  <button @click="isHappyModel = false">NO</button>
</template>

I understand that the point is to demonstrate Vue's syntax and feature in this specific scenario, but you should either change the example to a more practical one in which defineModel() isn't enough, or mention this feature below the current example.