How to set a custom type for context in v1.13?

In ky v1.12, this worked fine:
```ts
declare module 'ky' {
  interface Options {
    context?: MyContext;
  }
  interface NormalizedOptions {
    context?: MyContext;
  }
}
```

After upgrading to v1.13, I get this error:
> Subsequent property declarations must have the same type. Property ‘context’ must be of type ‘Record<string, unknown>’, but here has type ‘MyContext | undefined’.ts(2717)