Add initial project structure with Result type and extension methods

Rehlert.RoP/Result.cs

@@ -0,0 +1,13 @@
+using Dunet;
+
+namespace Rehlert.RoP;
+
+[Union]
+public partial record Result<TOk, TError>
+    where TOk : notnull
+    where TError : notnull
+{
+    public partial record Ok(TOk Value);
+
+    public partial record Error(TError Value);
+}