Add the player select applet. (#537)

This introduces the somewhat completed version of the Player Select
Applet, allowing users to select either a user or a guest from the UI.
Note: Selecting the guest more then once currently does not work.

closes https://github.com/Ryubing/Ryujinx/issues/532

src/Ryujinx/UI/ViewModels/UserSelectorDialogViewModel.cs

@@ -0,0 +1,14 @@
+using CommunityToolkit.Mvvm.ComponentModel;
+using Ryujinx.HLE.HOS.Services.Account.Acc;
+using System.Collections.ObjectModel;
+
+namespace Ryujinx.Ava.UI.ViewModels
+{
+    public partial class UserSelectorDialogViewModel : BaseModel
+    {
+
+        [ObservableProperty] private UserId _selectedUserId;
+
+        [ObservableProperty] private ObservableCollection<BaseModel> _profiles = [];
+    }
+}