Add iOS refresh instructions to README.

README.md

@@ -1377,6 +1377,13 @@ live:
       videoBufferSize: 41943040
 ```
 
+### Home Assistant iOS App not updating after card version change
+
+Try reseting the app frontend cache:
+
+* Navigate to 'iOS app settings' in the app.
+* Choose 'Reset frontend cache'.
+
 ## Development
 
 ### Building