SPIGOT-4339: Add EntityTransformEvent

Thanks klugemonkey for some contributions in https://hub.spigotmc.org/stash/projects/SPIGOT/repos/bukkit/pull-requests/351/overview

By: nathat890 <nathat890@outlook.com>

paper-server/src/main/java/org/bukkit/craftbukkit/event/CraftEventFactory.java

@@ -300,6 +300,16 @@ public class CraftEventFactory {
         return event;
     }
 
+    /**
+     * EntityTransformEvent
+     */
+    public static EntityTransformEvent callEntityTransformEvent(EntityLiving original, EntityLiving converted, EntityTransformEvent.TransformReason convertType) {
+        EntityTransformEvent event = new EntityTransformEvent(original.getBukkitEntity(), converted.getBukkitEntity(), convertType);
+        Bukkit.getPluginManager().callEvent(event);
+
+        return event;
+    }
+
     /**
      * EntityShootBowEvent
      */