SPIGOT-7831: Add CreatureSpawnEvent.SpawnReason#POTION_EFFECT

By: Doc <nachito94@msn.com>

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

@@ -205,6 +205,11 @@ public class CreatureSpawnEvent extends EntitySpawnEvent {
          * When a creature is spawned by an enchantment
          */
         ENCHANTMENT,
+        /**
+         * When a creature is spawned by a potion effect, for example:
+         * {@link org.bukkit.potion.PotionType#OOZING}, {@link org.bukkit.potion.PotionType#INFESTED}
+         */
+        POTION_EFFECT,
         /**
          * When a creature is spawned by plugins
          */