Ts类型别名

对已知的一些类型定义名称

type 类型名 = ...

# 举个例子
  type Gender = "男" | "女";
  type User = {
    name: string,
    age: number,
    gender: Gender
  }
  let u: User;
  u = {
    name: "sadas",
    gender: "男",
    age: 20
  }
  function getUsers(g: Gender): User[] {
    return [];
  }