feat(NextcloudKitUI): generic onboarding screen

Sources/NextcloudKitUI/Documentation.docc/Documentation.md

@@ -19,6 +19,11 @@ Key traits of this package:
 
 ## Topics
 
+### Onboarding
+
+- ``OnboardingView``
+- ``OnboardingFeature``
+
 ### Login
 
 - ``ServerAddressView``

Sources/NextcloudKitUI/Image+appIcon.swift

@@ -0,0 +1,23 @@
+// SPDX-FileCopyrightText: Nextcloud GmbH
+// SPDX-FileCopyrightText: 2026 Milen Pivchev
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+import SwiftUI
+
+extension Image {
+    ///
+    /// The app's own icon, loaded from the largest icon file the build lists in the Info.plist.
+    ///
+    public static var appIcon: Image? {
+        #if canImport(UIKit)
+        let icons = Bundle.main.object(forInfoDictionaryKey: "CFBundleIcons") as? [String: Any]
+        let primaryIcon = icons?["CFBundlePrimaryIcon"] as? [String: Any]
+
+        guard let name = (primaryIcon?["CFBundleIconFiles"] as? [String])?.last, let image = UIImage(named: name) else { return nil }
+
+        return Image(uiImage: image)
+        #else
+        return nil
+        #endif
+    }
+}