fix: AvaloniaVS can not resolve resource relative path in Previewer

src/Avalonia.DesignerSupport/DesignWindowLoader.cs

@@ -29,7 +29,7 @@ namespace Avalonia.DesignerSupport
                 if (assemblyPath != null)
                 {
                     if (xamlFileProjectPath == null)
-                        xamlFileProjectPath = "/Designer/Fake.xaml";
+                        xamlFileProjectPath = "/Fake.xaml";
                     //Fabricate fake Uri
                     baseUri =
                         new Uri($"avares://{Path.GetFileNameWithoutExtension(assemblyPath)}{xamlFileProjectPath}");
@@ -43,7 +43,7 @@ namespace Avalonia.DesignerSupport
                 {
                     LocalAssembly = localAsm,
                     DesignMode = true,
-                    UseCompiledBindingsByDefault = bool.TryParse(useCompiledBindings, out var parsedValue ) && parsedValue 
+                    UseCompiledBindingsByDefault = bool.TryParse(useCompiledBindings, out var parsedValue) && parsedValue
                 });
                 var style = loaded as IStyle;
                 var resources = loaded as ResourceDictionary;
@@ -90,14 +90,14 @@ namespace Avalonia.DesignerSupport
                         };
                 }
                 else if (loaded is Application)
-                    control = new TextBlock {Text = "Application can't be previewed in design view"};
+                    control = new TextBlock { Text = "Application can't be previewed in design view" };
                 else
-                    control = (Control) loaded;
+                    control = (Control)loaded;
 
                 window = control as Window;
                 if (window == null)
                 {
-                    window = new Window() {Content = (Control)control};
+                    window = new Window() { Content = (Control)control };
                 }
 
                 if (window.PlatformImpl is OffscreenTopLevelImplBase offscreenImpl)