Add Shulker Boxes (#3678)

this implementation is working, although incomplete:

- The shulker close sound should not be played until the end of the shulker closing animation, which takes approximately 1 second.
- An open shulker box has a different collision box than a closed one - it should be +0.5 in whichever direction the shulker is facing. (During the animation, the bounding box also dynamically changes size - you can see this in vanilla by shooting an arrow into the top of an open shulkerbox facing UP, and then closing it - the arrow will fall and collide with the lid multiple times.

However, resolving both of these issues requires significant internal changes which are beyond the scope of this PR.

src/block/inventory/ShulkerBoxInventory.php

@@ -0,0 +1,64 @@
+<?php
+
+/*
+ *
+ *  ____            _        _   __  __ _                  __  __ ____
+ * |  _ \ ___   ___| | _____| |_|  \/  (_)_ __   ___      |  \/  |  _ \
+ * | |_) / _ \ / __| |/ / _ \ __| |\/| | | '_ \ / _ \_____| |\/| | |_) |
+ * |  __/ (_) | (__|   <  __/ |_| |  | | | | | |  __/_____| |  | |  __/
+ * |_|   \___/ \___|_|\_\___|\__|_|  |_|_|_| |_|\___|     |_|  |_|_|
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * @author PocketMine Team
+ * @link http://www.pocketmine.net/
+ *
+ *
+*/
+
+declare(strict_types=1);
+
+namespace pocketmine\block\inventory;
+
+use pocketmine\block\BlockLegacyIds;
+use pocketmine\inventory\SimpleInventory;
+use pocketmine\item\Item;
+use pocketmine\network\mcpe\protocol\BlockEventPacket;
+use pocketmine\world\Position;
+use pocketmine\world\sound\ShulkerCloseSound;
+use pocketmine\world\sound\ShulkerOpenSound;
+use pocketmine\world\sound\Sound;
+
+class ShulkerBoxInventory extends SimpleInventory implements BlockInventory{
+	use AnimatedBlockInventoryTrait;
+
+	public function __construct(Position $holder){
+		$this->holder = $holder;
+		parent::__construct(27);
+	}
+
+	protected function getOpenSound() : Sound{
+		return new ShulkerOpenSound();
+	}
+
+	protected function getCloseSound() : Sound{
+		return new ShulkerCloseSound();
+	}
+
+	public function canAddItem(Item $item) : bool{
+		if($item->getId() === BlockLegacyIds::UNDYED_SHULKER_BOX || $item->getId() === BlockLegacyIds::SHULKER_BOX){
+			return false;
+		}
+		return parent::canAddItem($item);
+	}
+
+	protected function animateBlock(bool $isOpen) : void{
+		$holder = $this->getHolder();
+
+		//event ID is always 1 for a chest
+		$holder->getWorld()->broadcastPacketToViewers($holder, BlockEventPacket::create(1, $isOpen ? 1 : 0, $holder->asVector3()));
+	}
+}