Update samples

Assets/Samples~/ExtensionSample/Scripts/Editor/CustomPackRule.cs

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+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.IO;
+using UnityEngine;
+using YooAsset.Editor;
+
+/// <summary>
+/// 按照文件名的首字母来划分资源
+/// </summary>
+public class PackEffectTexture : IPackRule
+{
+	private const string PackDirectory = "Assets/Effect/Textures/";
+
+	string IPackRule.GetBundleName(PackRuleData data)
+	{
+		string assetPath = data.AssetPath;
+		if (assetPath.StartsWith(PackDirectory) == false)
+			throw new Exception($"Only support folder : {PackDirectory}");
+	
+		string assetName = Path.GetFileName(assetPath).ToLower();
+		string firstChar = assetName.Substring(0, 1);
+		return $"{PackDirectory}effect_texture_{firstChar}";
+	}
+}