Support asHtml()

When grouping e.g. a Textfield with `->asHtml()` this Field renders the html code.

Would be great if we can use `->asHtml()` for this field as well. I guess this would require something like this
`      <div v-if="field.asHtml" v-html="field.value"></div>
`

as found in

`vendor/laravel/nova/resources/js/components/Index/TextField.vue`