refactor: 💥 Scalar concept renamed to ScalableNumber

Resolves #114

src/include/units/customization_points.h

@@ -37,7 +37,7 @@ namespace units {
  * 
  * @tparam Rep a representation type for which a type trait is defined
  */
-template<Scalar Rep>
+template<ScalableNumber Rep>
 inline constexpr bool treat_as_floating_point = std::is_floating_point_v<Rep>;
 
 /**
@@ -49,7 +49,7 @@ inline constexpr bool treat_as_floating_point = std::is_floating_point_v<Rep>;
  * 
  * @tparam Rep a representation type for which a type trait is defined
  */
-template<Scalar Rep>
+template<ScalableNumber Rep>
 struct quantity_values {
   static constexpr Rep zero() noexcept { return Rep(0); }
   static constexpr Rep one() noexcept { return Rep(1); }