Fix Intefaces typo

src/addons/attach/Interfaces.ts

@@ -0,0 +1,18 @@
+/**
+ * Copyright (c) 2018 The xterm.js authors. All rights reserved.
+ * @license MIT
+ *
+ * Implements the attach method, that attaches the terminal to a WebSocket stream.
+ */
+
+import { Terminal } from 'xterm';
+
+export interface IAttachAddonTerminal extends Terminal {
+  __socket?: WebSocket;
+  __attachSocketBuffer?: string;
+
+  __getMessage?(ev: MessageEvent): void;
+  __flushBuffer?(): void;
+  __pushToBuffer?(data: string): void;
+  __sendData?(data: string): void;
+}