优化更新代码，添加界面功能并整合

WPFluent/Controls/FontIcon/FontIconFallback.cs

@@ -0,0 +1,26 @@
+using System.ComponentModel;
+using System.Windows;
+using System.Windows.Controls;
+using System.Windows.Media;
+
+namespace WPFluent.Controls;
+
+// TODO: Use font icon if available
+[EditorBrowsable(EditorBrowsableState.Never)]
+public sealed class FontIconFallback : Control
+{
+    static FontIconFallback()
+    {
+        DefaultStyleKeyProperty.OverrideMetadata(typeof(FontIconFallback), new FrameworkPropertyMetadata(typeof(FontIconFallback)));
+        FocusableProperty.OverrideMetadata(typeof(FontIconFallback), new FrameworkPropertyMetadata(false));
+    }
+
+    public static readonly DependencyProperty DataProperty =
+        DependencyProperty.Register(nameof(Data), typeof(Geometry), typeof(FontIconFallback), null);
+
+    public Geometry Data
+    {
+        get => (Geometry)GetValue(DataProperty);
+        set => SetValue(DataProperty, value);
+    }
+}