relationship ref should support multiple types

[RobertAlbus]

Relationship ref should support relationships to more than one type of but currently only takes a single string value. Could we extend this to take a string[] ?

export const Rendering = list({
  fields: {
    page: relationship({
      ref: 'Page.renderings',
    }),
    datasource: relationship({
      ref: ['Banner', 'RichText']        //  <==== like this!
    }),
  },
})

[bladey]

Thanks for the suggestion @RobertAlbus!