add onboarding tutorial + icon

Pocket Poster/Views/OnBoarding/OnBoardingView.swift

@@ -0,0 +1,18 @@
+//
+//  OnBoardingView.swift
+//  Pocket Poster
+//
+//  Created by lemin on 5/31/25.
+//
+
+import SwiftUI
+
+struct OnBoardingView: View {
+    @State var currentIndex: Int = 0
+    
+    var body: some View {
+        VStack {
+            OnBoardingCardView(info: onBoardingCards[currentIndex], pageCount: onBoardingCards.count, idx: $currentIndex)
+        }
+    }
+}