Define a Default Value for an Array of Items as a String with a Radio Layout

type: 'string',
options: {
    layout: 'radio',
    list: [
        { title: 'Left', value: 'left', default: true }, // here?
        { title: 'Right', value: 'right' }
    ],
}

fields: [
  {
    name: 'list',
    type: 'string',
    options: {
      layout: 'radio',
      list: [
        { title: 'Left', value: 'left' },
        { title: 'Right', value: 'right' },
      ],
    }
  },
],
initialValue: {
  list: 'left'
}

export default {
    name: 'project_screenshots',
    title: 'Screenshots',
    type: 'object',
    fields: [
        {
            name: 'type',
            title: 'Screenshot type',
            type: 'string',
            options: {
                list: [
                    { value: 'stack', title: 'Stacked' },
                    { value: 'two-cols', title: 'Two columns' },
                ],
                layout: 'radio',
                direction: 'horizontal',
            },
            initialValue: {
                list: 'left'
            },
            preview: {
                prepare ({ title }) {
                    return {
                        title: title.value
                    }
                }
            }
        },