优化更新代码，添加界面功能并整合

WPFluent/Controls/TreeGrid/TreeGridItem.cs

@@ -0,0 +1,12 @@
+
+
+
+// ReSharper disable once CheckNamespace
+namespace WPFluent.Controls;
+
+/// <summary>
+/// Work in progress.
+/// </summary>
+public class TreeGridItem : System.Windows.Controls.Control
+{
+}