modify

Signed-off-by: NLVB8189 <lvbai1@huawei.com>

zh-cn/application-dev/reference/apis/js-apis-WallpaperExtensionAbility.md

@@ -34,6 +34,7 @@ onCreate(want: object): void
 
 ```js
 import WallpaperExtensionAbility from '@ohos.WallpaperExtensionAbility';
+
 class WallpaperExt extends WallpaperExtensionAbility {
     onCreate(want) {
         console.log('onCreate, want:' + want.abilityName);
@@ -59,6 +60,7 @@ onWallpaperChange(wallpaperType: number): void
 
 ```js
 import WallpaperExtensionAbility from '@ohos.WallpaperExtensionAbility';
+
 class WallpaperExt extends WallpaperExtensionAbility {
     onWallpaperChange(wallpaperType) {
         console.log('onWallpaperChange, wallpaperType:' + wallpaperType);
@@ -78,6 +80,7 @@ onDestroy(): void
 
 ```js
 import WallpaperExtensionAbility from '@ohos.WallpaperExtensionAbility';
+
 class WallpaperExt extends WallpaperExtensionAbility {
     onDestroy() {
         console.log('onDestroy');