Как передать событие от дочернего компонента к родительскому?

const { createApp, ref, defineComponent } = Vue;

const app = createApp({
  setup() {
    const cartItemsCount = ref(0)

    // expose to template and other options API hooks
    return {
      cartItemsCount
    }
  }
});

app.component('item', defineComponent({
  template: '<button @click = "addToCart">Add to Cart</button>',
  methods: {
    addToCart() {
        this.$emit("addToCart");
    }
  }
}));

app.mount('#app')

<script src = "https://unpkg.com/vue@3/dist/vue.global.prod.js"></script>
<div id = "app">
  <div>
    Items added into the cart : {{ cartItemsCount }}
  </div>
  <item @add-to-cart = "cartItemsCount += 1"></item>
</div>