add fp2 sample

csharp-fp2/Domain/Money.cs

@@ -0,0 +1,8 @@
+namespace CsharpFp2.Domain;
+
+public sealed record Money(decimal Amount)
+{
+    public Money Add(Money other) => new(Amount + other.Amount);
+
+    public Money Subtract(Money other) => new(Amount - other.Amount);
+}