Introduce IntKeyedDictionary to improve performance.

Assets/Cryville/Crtr/EffectManager.cs

@@ -1,10 +1,10 @@
-using System.Collections.Generic;
+using Cryville.Common.Collections.Specialized;
 using UnityEngine;
 
 namespace Cryville.Crtr {
 	public class EffectManager {
-		readonly Dictionary<int, EffectGroup> _groups
-			= new Dictionary<int, EffectGroup>();
+		readonly IntKeyedDictionary<EffectGroup> _groups
+			= new IntKeyedDictionary<EffectGroup>();
 		public EffectManager(PdtSkin skin) {
 			foreach (var e in skin.effects) {
 				_groups.Add(e.Key.Key, new EffectGroup(e.Value));