feat: add PlateOption and PlateOptimizerResult data classes

OpenNest.Core/PlateOptimizerResult.cs

@@ -0,0 +1,12 @@
+using System.Collections.Generic;
+
+namespace OpenNest
+{
+    public class PlateOptimizerResult
+    {
+        public List<Part> Parts { get; set; } = new();
+        public PlateOption ChosenSize { get; set; }
+        public double NetCost { get; set; }
+        public double Utilization { get; set; }
+    }
+}

OpenNest.Core/PlateOption.cs

@@ -0,0 +1,11 @@
+namespace OpenNest
+{
+    public class PlateOption
+    {
+        public double Width { get; set; }
+        public double Length { get; set; }
+        public double Cost { get; set; }
+
+        public double Area => Width * Length;
+    }
+}