message: docs: add doc to Auth module
diff: @@ -3,6 +3,9 @@ import { fetchJson } from "@xmcl/net";
  import { Response } from "got";
  import { v4 } from "uuid";
  +/**
  + * The interface to login/logout user
  + */
  export interface Auth {
  /**
  * The minecraft client token, the launcher should persist this
  