add slider style

HandyControlDemo/UserControl/Styles/SliderDemoCtl.xaml.cs

@@ -0,0 +1,11 @@
+// ReSharper disable once CheckNamespace
+namespace HandyControlDemo.UserControl
+{
+    public partial class SliderDemoCtl
+    {
+        public SliderDemoCtl()
+        {
+            InitializeComponent();
+        }
+    }
+}