Update transition-duration.md

docs/uni-app-x/css/transition-duration.md

@@ -7,10 +7,13 @@
 
 <!-- CSSJSON.transition-duration.values -->
 
+#### App平台  
+App平台不支持指定多个时长。
+
 <!-- CSSJSON.transition-duration.defaultValue -->
 
 <!-- CSSJSON.transition-duration.unixTags -->
 
 <!-- CSSJSON.transition-duration.compatibility -->
 
-<!-- CSSJSON.transition-duration.reference -->
\ No newline at end of file
+<!-- CSSJSON.transition-duration.reference -->