How to define schema for site settings in Sanity Studio

import S from '@sanity/desk-tool/structure-builder';

export default () =>
    S.list()
        .title(`Content`)
        .items([
            S.listItem()
                .title(`Site settings`)
                .child(
                    S.editor()
                        .schemaType(`siteSettings`)
                        .documentId(`siteSettings`)
                ),
            // Add visual divider
            S.divider(),
            ...S.documentTypeListItems()
                    .filter( listItem => ![`siteSettings`].includes(listItem.getId() ))
        ])

...
import siteSettings from './documents/siteSettings'
...
export default createSchema({
  types: schemaTypes.concat([
    ...
    siteSettings,
    ...
  ])
})

...
import siteSettings from './documents/siteSettings'
...
export default createSchema({
  types: schemaTypes.concat([
    ...
    siteSettings,
    ...
  ])
})