Add ability to change player item in hand. Adds BUKKIT-3318

By: Patrick Seidel <psycowithespn1@aim.com>

paper-api/src/main/java/org/bukkit/event/player/PlayerItemHeldEvent.java

@@ -1,13 +1,15 @@
 package org.bukkit.event.player;
 
 import org.bukkit.entity.Player;
+import org.bukkit.event.Cancellable;
 import org.bukkit.event.HandlerList;
 
 /**
  * Fired when a player changes their currently held item
  */
-public class PlayerItemHeldEvent extends PlayerEvent {
+public class PlayerItemHeldEvent extends PlayerEvent implements Cancellable {
     private static final HandlerList handlers = new HandlerList();
+    private boolean cancel = false;
     private final int previous;
     private final int current;
 
@@ -35,6 +37,14 @@ public class PlayerItemHeldEvent extends PlayerEvent {
         return current;
     }
 
+    public boolean isCancelled() {
+        return cancel;
+    }
+
+    public void setCancelled(boolean cancel) {
+        this.cancel = cancel;
+    }
+
     @Override
     public HandlerList getHandlers() {
         return handlers;