feat: two argument explicit cast support added

example/measurement.cpp

@@ -131,7 +131,11 @@ void example()
   const auto t = si::time<si::second, measurement<double>>(measurement(1.2, 0.1));
 
   const Speed auto v1 = a * t;
+#if DOWNCAST_MODE == 0
+  std::cout << a << " * " << t << " = " << v1 << " = " << quantity_cast<si::dim_speed, si::kilometre_per_hour>(v1) << '\n';
+#else
   std::cout << a << " * " << t << " = " << v1 << " = " << quantity_cast<si::kilometre_per_hour>(v1) << '\n';
+#endif
 
   si::length<si::metre, measurement<double>> length(measurement(123., 1.));
   std::cout << "10 * " << length << " = " << 10 * length << '\n';