Initial work on a setup wizard

Setup wizard abstraction & architecture from TKMM

src/Ryujinx/Systems/SetupWizard/BaseSetupWizard.cs

@@ -0,0 +1,31 @@
+using Avalonia.Controls.Presenters;
+using Ryujinx.Ava.Common.Locale;
+using Ryujinx.Systems.SetupWizard;
+using System.Threading.Tasks;
+
+namespace Ryujinx.Ava.Systems.SetupWizard
+{
+    public abstract class BaseSetupWizard(ContentPresenter presenter)
+    {
+        /// <summary>
+        /// Define the logic and flow of this <see cref="BaseSetupWizard"/>.
+        /// </summary>
+        public abstract ValueTask Start();
+
+        protected ValueTask<bool> FirstPage()
+        {
+            SetupWizardPageBuilder builder = new(presenter, isFirstPage: true);
+
+            return builder
+                .WithTitle(LocaleKeys.SetupWizardFirstPageTitle)
+                .WithContent(LocaleKeys.SetupWizardFirstPageContent)
+                .WithActionContent(LocaleKeys.SetupWizardFirstPageAction)
+                .Show();
+        }
+
+        protected SetupWizardPageBuilder NextPage()
+        {
+            return new SetupWizardPageBuilder(presenter);
+        }
+    }
+}