docs: updated readme with the call to the newer and older mapping method

Author: amyskippy

README.md

@@ -36,7 +36,7 @@ public class MyClass
 
 var dataReader = new SqlCommand("SELECT * FROM MyTable", connection).ExecuteReader();
 
-List<MyClass> results = dataReader.ToMyClass(); // "ToMyClass" method is generated at compile time
+List<MyClass> results = dataReader.To<MyClass>();
 ```
 
 Some notes for the above
@@ -49,6 +49,14 @@ Some notes for the above
 * Properly maps `DBNull` to `null`.
 * Complex-type properties may not work.
 
+### Legacy Mapping Method
+
+The `To<T>()` method has been added to unify the method calls, however the previous version of this method is maintained for now.
+
+```csharp
+List<MyClass> results = dataReader.ToMyClass();
+```
+
 ## Bonus API: `SetPropertyByName`
 
 This package also adds a super fast `SetPropertyByName` extension method generated at compile time for your class.