Implement VERY basic configuration window and stacking

AetherBags/Configuration/GeneralSettings.cs

@@ -0,0 +1,16 @@
+using System.Numerics;
+using KamiToolKit.Classes;
+
+namespace AetherBags.Configuration;
+
+public class GeneralSettings
+{
+    public InventoryStackMode StackMode { get; set; } = InventoryStackMode.AggregateByItemId;
+    public bool DebugEnabled { get; set; } = false;
+}
+
+public enum InventoryStackMode : byte
+{
+    NaturalStacks = 0,
+    AggregateByItemId = 1,
+}

AetherBags/Configuration/SystemConfiguration.cs

@@ -7,6 +7,8 @@ public class SystemConfiguration
 {
     public const string FileName = "AetherBags.json";
 
-    public CurrencySettings Currency { get; set; } = new();
+
+    public GeneralSettings General { get; set; } = new();
     public CategorySettings Categories { get; set; } = new();
+    public CurrencySettings Currency { get; set; } = new();
 }