SPIGOT-3110: SHULKER_BOX InventoryType

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

paper-api/src/main/java/org/bukkit/event/inventory/InventoryType.java

@@ -70,6 +70,10 @@ public enum InventoryType {
      * A hopper inventory, with 5 slots of type CONTAINER.
      */
     HOPPER(5, "Item Hopper"),
+    /**
+     * A shulker box inventory, with 27 slots of type CONTAINER.
+     */
+    SHULKER_BOX(27, "container.shulkerBox"),
     ;
 
     private final int size;