How to seed/upload images in KeystoneJS 6?

Question

Using the example here, if I then add an image field to Post:

// schema.ts
import { list } from '@keystone-6/core';
import { select, relationship, text, timestamp } from '@keystone-6/core/fields';

export const lists = {
  Post: list({
    fields: {
       featureImage: image(),
    }),
    /* ... */
  },
  /* ... */
});

How can I then adjust the seed/index.ts file to upload an image form the local drive?

// seed/index.ts
await context.query.Post.createOne({
    data: {
        ...postData,
        featureImage: { /* ??? What goes here ??? */ }
    },
    query: 'id',
});

Or otherwise, how can I programmatically add images so that keystonejs is aware of them?