Update .env.example

Author: ruskibenya

.env.example

@@ -8,3 +8,6 @@ VONAGE_PRIVATE_KEY='./private.key'
 
 # Your ngrok URL, don't include the protocol (https://)
 VONAGE_SERVER_HOSTNAME=''
+
+# RCS Brand Name, check formatting requirements. For instance, no spaces allowed
+RCS_SENDER_ID=''