Add SliderWithCallback component (#938)

Add SliderOption::on_change.

Useful to observe a change to the value.

Signed-off-by: Mikołaj Lubiak <lubiak@proton.me>
Co-authored-by: ArthurSonzogni <sonzogniarthur@gmail.com>

include/ftxui/component/component_options.hpp

@@ -227,6 +227,7 @@ struct SliderOption {
   Direction direction = Direction::Right;
   Color color_active = Color::White;
   Color color_inactive = Color::GrayDark;
+  std::function<void()> on_change;  ///> Called when `value` is updated.
 };
 
 // Parameter pack used by `WindowOptions::render`.