add delete menu

MultiChrono/ContentView.swift

@@ -156,6 +156,15 @@ struct StopwatchListItem: View {
         .padding(.vertical, 8)
         .background(Color(UIColor.systemBackground))
         .contentShape(Rectangle())
+        .contextMenu {
+            Button(role: .destructive) {
+                withAnimation {
+                    viewModel.deleteStopwatch(id: stopwatch.id)
+                }
+            } label: {
+                Label("Delete", systemImage: "trash")
+            }
+        }
         .onDrag {
             self.draggingStopwatch = stopwatch
             return NSItemProvider(object: stopwatch.id.uuidString as NSString)