优化更新代码，添加界面功能并整合

WPFluent/Appearance/ApplicationTheme.cs

@@ -0,0 +1,35 @@
+
+
+
+namespace WPFluent.Appearance;
+
+/// <summary>
+/// Theme in which an application using WPF UI is displayed.
+/// </summary>
+public enum ApplicationTheme
+{
+    /// <summary>
+    /// Sync application theme.
+    /// </summary>
+    Auto,
+
+    /// <summary>
+    /// Unknown application theme.
+    /// </summary>
+    Unknown,
+
+    /// <summary>
+    /// Dark application theme.
+    /// </summary>
+    Dark,
+
+    /// <summary>
+    /// Light application theme.
+    /// </summary>
+    Light,
+
+    /// <summary>
+    /// High contract application theme.
+    /// </summary>
+    HighContrast,
+}