Update transition-timing-function.md

docs/uni-app-x/css/transition-timing-function.md

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