Checkbox button debounce (#774)

This fixes: https://github.com/ArthurSonzogni/FTXUI/issues/773

Dragging the mouse with the left button pressed now avoids activating multiple
checkboxes.

Add support for detecting mouse press transition. Added:
```cpp
// The previous mouse event.
Mouse Mouse::previous;

// Return whether the mouse transitionned from:
// released to pressed => IsPressed()
// pressed to pressed => IsHeld()
// pressed to released => IsReleased()
bool Mouse::IsPressed(Button button) const;
bool Mouse::IsHeld(Button button) const;
bool Mouse::IsReleased(Button button) const;
```
A couple of components are now activated when the mouse is pressed,
as opposed to released.

Co-authored-by: ArthurSonzogni <sonzogniarthur@gmail.com>

include/ftxui/component/mouse.hpp

@@ -23,6 +23,11 @@ struct Mouse {
     Pressed = 1,
   };
 
+  // Utility function to check the variations of the mouse state.
+  bool IsPressed(Button btn = Left) const;   // Released => Pressed.
+  bool IsHeld(Button btn = Left) const;      // Pressed => Pressed.
+  bool IsReleased(Button btn = Left) const;  // Pressed => Released.
+
   // Button
   Button button = Button::None;
 
@@ -37,6 +42,9 @@ struct Mouse {
   // Coordinates:
   int x = 0;
   int y = 0;
+
+  // Previous mouse event, if any.
+  Mouse* previous = nullptr;
 };
 
 }  // namespace ftxui

include/ftxui/component/screen_interactive.hpp

@@ -112,6 +112,7 @@ class ScreenInteractive : public Screen {
 
   bool frame_valid_ = false;
 
+  Mouse latest_mouse_event_;
   friend class Loop;
 
  public: