如何在Vue-Toasted中添加css？

npm install vue-toasted --save

import Vue from 'vue'
import Toasted from 'vue-toasted'

Vue.use(Toasted)

methods: {
  showToast() {
    this.$toasted.show('Hello World!', {
      theme: 'toasted-primary',
      position: 'top-right',
      duration: 3000
    })
  }
}

<template>
  <div>
    <button @click="showToast">Show Toast</button>
  </div>
</template>

.toasted-primary {
  background-color: #337ab7;
  color: #fff;
}