Added function to read persisted sudoku

SudokuSolver/Program.cs

@@ -1,2 +1,16 @@
-// See https://aka.ms/new-console-template for more information
-Console.WriteLine("Hello, World!");
+namespace SudokuSolver;
+
+using System;
+
+public class EntryPoint{
+    public static void Main(string[] args){
+        foreach (var x in System.Environment.GetEnvironmentVariables()){
+            Console.WriteLine(x);
+        }
+
+        // It might be necessary to modify path.
+        RawSudokuGrid grid = RawSudokuGrid.LoadFile("../data/sudoku_001.json");
+        Console.WriteLine(grid);
+    }
+
+}