Move files for better organization

src/MainWindow.axaml.cs

@@ -0,0 +1,19 @@
+using Avalonia.Controls;
+using ReceiptPDFBuilder.Interfaces;
+using ReceiptPDFBuilder.ViewModels;
+
+namespace ReceiptPDFBuilder;
+
+public partial class MainWindow : Window, ITopLevelGrabber
+{
+    public MainWindow()
+    {
+        InitializeComponent();
+        DataContext = new MainWindowViewModel(this);
+    }
+
+    public TopLevel GetTopLevel()
+    {
+        return this;
+    }
+}