Adding MQTTv5 option to issue template

Author: jpwsutton

.github/ISSUE_TEMPLATE.md

@@ -2,5 +2,6 @@ Please fill out the form below before submitting, thank you!
 
 - [ ] Bug exists Release Version 1.2.0 ( Master Branch)
 - [ ] Bug exists in Snapshot Version 1.2.1-SNAPSHOT (Develop Branch)
+- [ ] Bug exists in MQTTv5 Version (mqttv5-new Branch)
 
 If this is a bug regarding the Android Service, please raise the bug here instead: https://github.com/eclipse/paho.mqtt.android/issues/new