trackball deceleration rate implementation

VoidLink/Input/CustomOSC/OnScreenButtonState.h

@@ -32,6 +32,7 @@ NS_ASSUME_NONNULL_BEGIN
 @property (nonatomic, assign) CGFloat borderWidth; // for OnScreenWidgetView
 @property (nonatomic, assign) CGFloat sensitivityFactorX; // for OnScreenWidgetView
 @property (nonatomic, assign) CGFloat sensitivityFactorY; // for OnScreenWidgetView
+@property (nonatomic, assign) CGFloat decelerationRate; // for OnScreenWidgetView
 @property (nonatomic, assign) CGFloat stickIndicatorOffset; // for OnScreenWidgetView
 @property (nonatomic, assign) CGFloat minStickOffset; // for OnScreenWidgetView
 @property NSString* widgetShape; // for OnScreenWidgetView