优化更新代码，添加界面功能并整合

WPFluent/Controls/VirtualizingPanel/SpacingMode.cs

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+
+
+
+/* Based on VirtualizingWrapPanel created by S. Bäumlisberger licensed under MIT license.
+   https://github.com/sbaeumlisberger/VirtualizingWrapPanel
+   Copyright (C) S. Bäumlisberger
+   All Rights Reserved. */
+
+namespace WPFluent.Controls;
+
+/// <summary>
+/// Specifies how remaining space is distributed. <para>Based on <see
+/// href="https://github.com/sbaeumlisberger/VirtualizingWrapPanel"/>.</para>
+/// </summary>
+public enum SpacingMode
+{
+    /// <summary>
+    /// Spacing is disabled and all items will be arranged as closely as possible.
+    /// </summary>
+    None,
+
+    /// <summary>
+    /// The remaining space is evenly distributed between the items on a layout row, as well as the start and end of
+    /// each row.
+    /// </summary>
+    Uniform,
+
+    /// <summary>
+    /// The remaining space is evenly distributed between the items on a layout row, excluding the start and end of each
+    /// row.
+    /// </summary>
+    BetweenItemsOnly,
+
+    /// <summary>
+    /// The remaining space is evenly distributed between start and end of each row.
+    /// </summary>
+    StartAndEndOnly,
+}