Ok() - minor consistency improvements

Author: space-alien

CSharpFunctionalExtensions/Result/Methods/Ok.cs

@@ -7,19 +7,19 @@ public partial struct Result
         [DebuggerStepThrough]
         public static Result Ok()
         {
-            return new Result(false, null);
+            return new Result(false, default);
         }
 
         [DebuggerStepThrough]
         public static Result<T> Ok<T>(T value)
         {
-            return new Result<T>(false, value, null);
+            return new Result<T>(false, value, default);
         }
 
         [DebuggerStepThrough]
         public static Result<T, E> Ok<T, E>(T value)
         {
-            return new Result<T, E>(false, value, default(E));
+            return new Result<T, E>(false, value, default);
         }
     }
 }