Finish logic around placing pieces from the hand.

Shogi.Domain/ValueObjects/Move.cs

@@ -3,6 +3,20 @@
 /// <summary>
 /// Represents a single piece being moved by a player from <paramref name="From"/> to <paramref name="To"/>.
 /// </summary>
-public record struct Move(Vector2 From, Vector2 To)
+public readonly record struct Move
 {
+    public Move(Vector2 from, Vector2 to)
+    {
+        From = from;
+        To = to;
+    }
+    public Move(WhichPiece pieceFromHand, Vector2 to)
+    {
+        PieceFromHand = pieceFromHand;
+        To = to;
+    }
+
+    public Vector2? From { get; }
+    public Vector2 To { get; }
+    public WhichPiece PieceFromHand { get; }
 }