SPIGOT-2127: Add DamageCause.ENTITY_SWEEP_ATTACK

By: md_5 <git@md-5.net>

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

@@ -287,6 +287,12 @@ public class EntityDamageEvent extends EntityEvent implements Cancellable {
          * Damage: variable
          */
         ENTITY_ATTACK,
+        /**
+         * Damage caused when an entity attacks another entity in a sweep attack.
+         * <p>
+         * Damage: variable
+         */
+        ENTITY_SWEEP_ATTACK,
         /**
          * Damage caused when attacked by a projectile.
          * <p>