Update README.md

Author: SoftwareJoint - Erlang, XMPP, Ejabberd & Servers

README.md

@@ -17,8 +17,10 @@ __BINARY_API:__  This lib supports http2. Check [using Legacy Binary API](https:
 - Erlang R21
 
 ### Note:
-apns_topic is app bundle identifier
+_apns_topic_ is app bundle identifier
+
 voip notifications append '.voip' > !apple! undocumented
+
 https://stackoverflow.com/questions/40301655/voip-push-with-new-token-based-auth
 
 ### How to compile: