fixed: toh-pt6

public/docs/ts/latest/tutorial/toh-pt6.jade

@@ -156,6 +156,8 @@ block backend
     The `forRoot` configuration method takes an `InMemoryDataService` class 
     that will prime the in-memory database as follows:
 
+    `forRoot`配置方法需要`InMemoryDataService`类实例，用来向内存数据库添加种子数据：
+
 +makeExample('app/in-memory-data.service.ts', 'init')(format='.')
 
 p This file replaces the #[code #[+adjExPath('mock-heroes.ts')]] which is now safe to delete.