[Constellation] Added support for the HelloEvent

Author: MJRLegends

src/main/java/com/mixer/api/resource/constellation/AbstractConstellationEvent.java

@@ -1,6 +1,7 @@
 package com.mixer.api.resource.constellation;
 
 import com.google.gson.annotations.SerializedName;
+import com.mixer.api.resource.constellation.events.HelloEvent;
 import com.mixer.api.resource.constellation.events.LiveEvent;
 
 public abstract class AbstractConstellationEvent<T extends AbstractConstellationEvent.EventData> extends AbstractConstellationDatagram {
@@ -13,7 +14,8 @@ public AbstractConstellationEvent() {
 
     public static abstract class EventData {}
     public static enum EventType {
-        @SerializedName("live") LIVE (LiveEvent.class);
+        @SerializedName("live") LIVE (LiveEvent.class),
+        @SerializedName("hello") HELLO (HelloEvent.class),
 
         private final Class<? extends AbstractConstellationEvent> correspondingClass;