Added 3D Variant, still nedds improvment

GameOfLife3D/GameModel/Cell.cs

@@ -0,0 +1,19 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace GameOfLife3D.GameModel
+{
+    internal struct Cell
+    {
+        public bool isAlive;
+        public int X, Y, Z;
+
+        public override string ToString()
+        {
+            return $"{X}:{Y}:{Z}::{isAlive}";
+        }
+    }
+}