feat: on-screen widget border alpha tweak

VoidLink/Input/CustomOSC/OnScreenButtonState.h

@@ -45,6 +45,7 @@ NS_ASSUME_NONNULL_BEGIN
 @property (nonatomic, assign) CGFloat oscLayerSizeFactor; // for OnScreenController CALayer
 @property (nonatomic, assign) CGFloat backgroundAlpha;
 @property (nonatomic, assign) CGFloat labelAlpha;
+@property (nonatomic, assign) CGFloat borderAlpha;
 @property (nonatomic, assign) uint8_t vibrationStyle;
 @property (nonatomic, assign) uint8_t mouseButtonAction;
 @property (nonatomic, assign) uint16_t autoTapInterval;