Implemented the UnavailableView view in the UI library.

Libraries/UI/Kit/Sources/Views/UnavailableView.swift

@@ -0,0 +1,105 @@
+//
+//  UnavailableView.swift
+//  ReviewsUIKit
+//
+//  Created by Javier Cicchelli on 22/03/2024.
+//  Copyright © 2024 Röck+Cöde VoF. All rights reserved.
+//
+
+import SwiftUI
+
+public struct UnavailableView: View {
+    
+    // MARK: Constants
+    private let description: String
+    private let systemImage: String
+    private let title: String
+
+    private let action: (() -> Void)?
+    private let button: String?
+
+    // MARK: Initialisers
+    public init(
+        systemImage: String,
+        title: String,
+        description: String,
+        button: String? = nil,
+        action: (() -> Void)? = nil
+    ) {
+        self.action = action
+        self.button = button
+        self.description = description
+        self.systemImage = systemImage
+        self.title = title
+    }
+
+    // MARK: Body
+    public var body: some View {
+        if #available(iOS 17.0, *) {
+            if let button, let action {
+                ContentUnavailableView {
+                    Label(title, systemImage: systemImage)
+                } description: {
+                    Text(description)
+                } actions: {
+                    Button(action: action) {
+                        Text(button)
+                    }
+                }
+            } else {
+                ContentUnavailableView(
+                    title,
+                    systemImage: systemImage,
+                    description: Text(description)
+                )
+            }
+        } else {
+            VStack(spacing: 24) {
+                Image(systemName: systemImage)
+                    .resizable()
+                    .frame(width: 52, height: 52)
+                    .foregroundColor(.secondary)
+
+                VStack {
+                    Text(title)
+                        .font(.title2.bold())
+                        .foregroundColor(.primary)
+                    
+                    Text(description)
+                        .font(.subheadline)
+                        .foregroundColor(.secondary)
+                }
+                .multilineTextAlignment(.center)
+                
+                if let button, let action {
+                    Button(action: action) {
+                        Text(button)
+                            .font(.subheadline)
+                    }
+                }
+            }
+            .padding(.horizontal, 52)
+        }
+    }
+    
+}
+
+// MARK: - Previews
+#Preview("Unavailable View with image, title, and description") {
+    UnavailableView(
+        systemImage: "star",
+        title: "Some title goes here...",
+        description: "Some long, explanatory description goes in here..."
+    )
+}
+
+#Preview("Unavailable View with image, title, description, button, and action") {
+    UnavailableView(
+        systemImage: "star",
+        title: "Some title goes here...",
+        description: "Some long, explanatory description goes in here...",
+        button: "Some button text here..."
+    ) {
+        // On action closure.
+    }
+}