Save/load settings, Move about window to dialog

ViewModels/AboutViewModel.cs

@@ -0,0 +1,33 @@
+#nullable enable
+
+using System;
+using System.Collections.ObjectModel;
+using System.Globalization;
+using System.IO;
+using System.Linq;
+using System.Threading.Tasks;
+using Avalonia.Platform.Storage;
+using Avalonia.Themes.Fluent;
+using DialogHostAvalonia;
+using ImageMagick;
+using MigraDoc.DocumentObjectModel;
+using MigraDoc.Rendering;
+using PdfSharp.Fonts;
+using PdfSharp.Pdf.IO;
+using PdfSharp.Snippets.Font;
+using ReceiptPDFBuilder.Interfaces;
+using ReceiptPDFBuilder.Models;
+
+namespace ReceiptPDFBuilder.ViewModels;
+
+class AboutViewModel
+{
+    public AboutViewModel()
+    {
+    }
+
+    public void Close()
+    {
+        DialogHost.Close("DialogHost", null);
+    }
+}