add onboarding tutorial + icon

Pocket Poster/Views/OnBoarding/OnBoardingPage.swift

@@ -0,0 +1,57 @@
+//
+//  OnBoardingPage.swift
+//  Pocket Poster
+//
+//  Created by lemin on 5/31/25.
+//
+
+import SwiftUICore
+
+struct OnBoardingPage: Identifiable {
+    var id = UUID()
+    var title: String
+    var description: String
+    var image: String
+    var link: URL?
+    var linkName: String?
+    var gradientColors: [Color]
+    
+    init(title: String, description: String, image: String, link: URL? = nil, linkName: String? = nil, gradientColors: [Color] = [Color("WelcomeLight"), Color("WelcomeDark")]) {
+        self.id = UUID()
+        self.title = title
+        self.description = description
+        self.image = image
+        self.link = link
+        self.linkName = linkName
+        self.gradientColors = gradientColors
+    }
+}
+
+let onBoardingCards: [OnBoardingPage] = [
+    .init(
+        title: "Welcome to Pocket Poster!",
+        description: "Here is a tutorial to help you get started with the app.",
+        image: "Logo"
+    ),
+    .init(
+        title: "Install the Shortcut",
+        description: "To apply, you will need a shortcut that opens PosterBoard.",
+        image: "Shortcuts",
+        link: URL(string: "https://www.icloud.com/shortcuts/9035ef1d51c247dba8c9861dc10b4aa7"),
+        linkName: "Get Shortcut"
+    ),
+    .init(
+        title: "Install Nugget",
+        description: "To get the app bundle id, Nugget is required.\n\nOn your computer, download Nugget from the GitHub.",
+        image: "Nugget",
+        link: URL(string: "https://github.com/leminlimez/Nugget/releases/latest"),
+        linkName: "Open GitHub"
+    ),
+    .init(
+        title: "Enjoy!",
+        description: "You can find wallpapers on the official Cowabun.ga website.",
+        image: "Cowabunga",
+        link: URL(string: "https://cowabun.ga/wallpapers"),
+        linkName: "Find Wallpapers"
+    )
+]