Doc errors for Assign

[webberwang]

import { Assign } from 'utility-types';

type Props = { name: string; age: number; visible: boolean };
type NewProps = { age: string; other: string };

// Expect: { name: string; age: number; visible: boolean; other: string; }
type ExtendedProps = Assign<Props, NewProps>;

// Expect: { name: string; age: STRING; visible: boolean; other: string; }