Improve troubleshooting text to say uuid.v4()

Author: sanjaypojo

README.md

@@ -668,7 +668,7 @@ adb logcat *:S RNCallKeepModule:V
 ```
 
 ## Troubleshooting
-- Ensure that you use a valid `uuid` using the uuid library as shown in the examples (not a custom string), otherwise the incoming call screen will never be shown on iOS.
+- Ensure that you construct a valid `uuid` by importing the `uuid` library and running `uuid.v4()` as shown in the examples. If you don't do this and use a custom string, the incoming call screen will never be shown on iOS.
 
 ## Contributing