addConstructorVariadic
Add a constructor to @jsc_class. If @name is null, the class name will be used. When
This function creates the constructor, which needs to be added to an object as a property to be able to use it. Use jsc_context_set_value() to make the constructor available in the global object.
Note that the value returned by @callback is adopted by @jsc_class, and the #GDestroyNotify passed to jsc_context_register_class() is responsible for disposing of it.
Return
a #JSCValue representing the class constructor.
Parameters
the constructor name or null
a #GCallback to be called to create an instance of @jsc_class
the #GType of the constructor return value