I want to give the tr and td a class name in my Vuetify data-table. But what am I doing wrong as this isn't working while I see everywhere this solution.

```
<template>
  <v-data-table :headers="headers" :items="customers" class="elevation-1">
    <template slot="items" slot-scope="props">
      <td class="test">{{ props.item.name}}</td>
      <td class="test1">{{ props.item.telephone}}</td>
      <td class="test2">{{ props.item.email}}</td>
      <td class="test3">{{ props.item.website}}</td>
      <td class="test4">{{ props.item.location}}</td>
    </template>
  </v-data-table>
</template>

```