ServiceExtensionAbility开发指导错误示例代码修改

Signed-off-by: NHuangXW <huangxinwei4@huawei.com>

zh-cn/application-dev/ability/stage-serviceextension.md

@@ -42,7 +42,9 @@ OpenHarmony当前不支持三方应用创建ServiceExtensionAbility。
 2. 开发者在定义Service的目录下创建TS文件，自定义类继承ServiceExtensionAbility，重写基类回调函数，示例如下：
 
     ```js
+    import ServiceExtensionAbility from '@ohos.application.ServiceExtensionAbility'
     import rpc from '@ohos.rpc'
+
     class StubTest extends rpc.RemoteObject {
         constructor(des) {
             super(des);
@@ -51,7 +53,8 @@ OpenHarmony当前不支持三方应用创建ServiceExtensionAbility。
         }
     }
 
-    class ServiceExt extends ServiceExtensionAbility {
+    class ServiceExtAbility extends ServiceExtensionAbility {
+        onCreate(want) {
             console.log('onCreate, want:' + want.abilityName);
         }
         onRequest(want, startId) {