Added new MELTING DamageCause. Addresses BUKKIT-1244

By: EvilSeph <evilseph@gmail.com>

paper-api/src/main/java/org/bukkit/event/entity/EntityDamageEvent.java

@@ -117,6 +117,12 @@ public class EntityDamageEvent extends EntityEvent implements Cancellable {
          * Damage: 1
          */
         FIRE_TICK,
+        /**
+         * Damage caused due to a snowman melting
+         * <p />
+         * Damage: 1
+         */
+        MELTING,
         /**
          * Damage caused by direct exposure to lava
          * <p />