在ionic 4中的toast控制器中加入字体的图标

import { ToastController } from '@ionic/angular';

constructor(private toastController: ToastController) { }

async presentToast() {
  const toast = await this.toastController.create({
    message: '这是一个带图标的Toast',
    duration: 2000,
    position: 'bottom',
    buttons: [
      {
        side: 'start',
        icon: 'heart',
        text: '喜欢',
        handler: () => {
          console.log('喜欢按钮被点击');
        }
      },
      {
        text: '关闭',
        role: 'cancel',
        handler: () => {
          console.log('关闭按钮被点击');
        }
      }
    ]
  });
  toast.present();
}