Add project files.

Views/Windows/MainWindow.xaml

@@ -0,0 +1,65 @@
+<ui:FluentWindow
+    x:Class="DownloadManager.Views.Windows.MainWindow"
+    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+    xmlns:local="clr-namespace:DownloadManager.Views.Windows"
+    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+    xmlns:ui="http://schemas.lepo.co/wpfui/2022/xaml"
+    Title="{Binding ViewModel.ApplicationTitle, Mode=OneWay}"
+    Width="1100"
+    Height="650"
+    d:DataContext="{d:DesignInstance local:MainWindow,
+                                     IsDesignTimeCreatable=True}"
+    d:DesignHeight="450"
+    d:DesignWidth="800"
+    ui:Design.Background="{DynamicResource ApplicationBackgroundBrush}"
+    ui:Design.Foreground="{DynamicResource TextFillColorPrimaryBrush}"
+    ExtendsContentIntoTitleBar="True"
+    Foreground="{DynamicResource TextFillColorPrimaryBrush}"
+    WindowBackdropType="Mica"
+    WindowCornerPreference="Round"
+    WindowStartupLocation="CenterScreen"
+    mc:Ignorable="d">
+    <Grid>
+        <Grid.RowDefinitions>
+            <RowDefinition Height="Auto" />
+            <RowDefinition Height="*" />
+        </Grid.RowDefinitions>
+        <ui:NavigationView
+            x:Name="RootNavigation"
+            Grid.Row="1"
+            Padding="42,0,42,0"
+            BreadcrumbBar="{Binding ElementName=BreadcrumbBar}"
+            FooterMenuItemsSource="{Binding ViewModel.FooterMenuItems, Mode=OneWay}"
+            FrameMargin="0"
+            IsBackButtonVisible="Visible"
+            IsPaneToggleVisible="True"
+            MenuItemsSource="{Binding ViewModel.MenuItems, Mode=OneWay}"
+            PaneDisplayMode="LeftFluent">
+            <ui:NavigationView.Header>
+                <ui:BreadcrumbBar x:Name="BreadcrumbBar" Margin="42,32,42,20" />
+            </ui:NavigationView.Header>
+            <ui:NavigationView.ContentOverlay>
+                <Grid>
+                    <ui:SnackbarPresenter x:Name="SnackbarPresenter" />
+                </Grid>
+            </ui:NavigationView.ContentOverlay>
+        </ui:NavigationView>
+
+        <ContentPresenter
+            x:Name="RootContentDialog"
+            Grid.Row="0"
+            Grid.RowSpan="2" />
+
+        <ui:TitleBar
+            x:Name="TitleBar"
+            Title="{Binding ViewModel.ApplicationTitle}"
+            Grid.Row="0"
+            CloseWindowByDoubleClickOnIcon="True">
+            <ui:TitleBar.Icon>
+                <ui:ImageIcon Source="pack://application:,,,/Assets/wpfui-icon-256.png" />
+            </ui:TitleBar.Icon>
+        </ui:TitleBar>
+    </Grid>
+</ui:FluentWindow>