fix(spigot): opening book programmatically

Fixes #435

core/src/main/java/com/rexcantor64/triton/packetinterceptor/ProtocolLibListener.java

@@ -172,6 +172,8 @@ private void setupPacketHandlers() {
         }
         packetHandlers.put(PacketType.Play.Server.WINDOW_ITEMS, asAsync(this::handleWindowItems));
         packetHandlers.put(PacketType.Play.Server.SET_SLOT, asAsync(this::handleSetSlot));
+        // Nothing to translate, but register listener to ensure order in async mode
+        packetHandlers.put(PacketType.Play.Server.OPEN_BOOK, asAsync(this::handleNop));
         if (MinecraftVersion.CAVES_CLIFFS_2.atOrAbove()) { // 1.18+
             // While the villager merchant interface redesign was on 1.14, the Bukkit API only has all fields on 1.18
             packetHandlers.put(PacketType.Play.Server.OPEN_WINDOW_MERCHANT, asAsync(this::handleMerchantItems));
@@ -723,6 +725,14 @@ private void handleDeathScreen(PacketEvent packet, SpigotLanguagePlayer language
         packet.getPacket().getChatComponents().writeSafely(0, component);
     }
 
+    /**
+     * No-operation function, used to simply register a packet listener in order to ensure certain packets
+     * are sent in order when using async mode.
+     */
+    private void handleNop(PacketEvent packet, SpigotLanguagePlayer languagePlayer) {
+        // nop
+    }
+
     /* PROTOCOL LIB */
 
     @Override