migrate to svg symbols & add maintenance info

ModpackUpdater/AppSymbolFactory.cs

@@ -0,0 +1,19 @@
+using Pilz.UI.Telerik;
+using System.Reflection;
+
+namespace ModpackUpdater;
+
+public class AppSymbolFactory : SymbolFactory<AppSymbols>
+{
+    public static AppSymbolFactory Instance { get; } = new();
+
+    public override Assembly GetSvgImageResourceAssembly()
+    {
+        return Assembly.GetExecutingAssembly();
+    }
+
+    public override string GetSvgImageRessourcePath(AppSymbols svgImage)
+    {
+        return $"{GetType().Namespace}.Symbols.{svgImage}.svg";
+    }
+}