Fix itemWidth return negative value

Resolved runtime warning "[SwiftUI] Invalid frame dimension (negative or non-finite)"

Sources/ACarousel/ACarouselViewModel.swift

@@ -140,7 +140,7 @@ extension ACarouselViewModel {
     }
     
     var itemWidth: CGFloat {
-        viewSize.width - defaultPadding * 2
+        max(0, viewSize.width - defaultPadding * 2)
     }
     
     var timer: TimePublisher? {