Remove hardcode (Rogue3D_SelectDiff)

Common/Data/Excel/Rogue3DDifficultExcel.cs

@@ -0,0 +1,17 @@
+using Newtonsoft.Json;
+
+namespace MikuSB.Data.Excel;
+
+[ResourceEntity("server_01_difficult.json")]
+public class Rogue3DDifficultExcel : ExcelResource
+{
+    [JsonProperty("DifficultID")] public uint DifficultId { get; set; }
+    [JsonProperty("GameplayGroup")] public List<uint> GameplayGroup { get; set; } = [];
+
+    public override uint GetId() => DifficultId;
+
+    public override void Loaded()
+    {
+        GameData.Rogue3DDifficultData[DifficultId] = this;
+    }
+}