add NotifyIcon and Notification docs

doc/source/handycontrol/extend_controls/notification/index.md

@@ -1,3 +1,54 @@
 ---
-title: Notification
+title: Notification 桌面通知
 ---
+
+用于在桌面显示一则富内容消息.
+
+```cs
+public sealed class Notification : System.Windows.Window
+```
+
+# 方法
+
+|名称|说明|
+|-|-|
+| Show(object, ShowAnimation, bool) | 显示桌面通知(消息内容, 动画效果类型, 是否保持打开) |
+
+# 案例
+
+```xml
+<Border x:Class="HandyControlDemo.UserControl.AppNotification"
+        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+        xmlns:hc="https://handyorg.github.io/handycontrol"
+        Background="White"
+        BorderThickness="1"
+        BorderBrush="{DynamicResource BorderBrush}"
+        Width="320"
+        Height="518">
+    <hc:SimplePanel>
+        <Path Margin="0,36,0,0" VerticalAlignment="Top" Width="70" Height="70" Data="{StaticResource LogoGeometry}" Fill="#f06632"/>
+        <TextBlock Text="HandyControl" FontSize="30" Foreground="{StaticResource PrimaryBrush}" HorizontalAlignment="Center" Margin="0,122,0,0" VerticalAlignment="Top"/>
+        <Button Command="hc:ControlCommands.CloseWindow" CommandParameter="{Binding RelativeSource={RelativeSource Self}}" Content="{hc:Lang Key={x:Static hc:LangKeys.Close}}" HorizontalAlignment="Stretch" VerticalAlignment="Bottom" Margin="10,0,10,10"/>
+    </hc:SimplePanel>
+</Border>
+```
+
+```cs
+namespace HandyControlDemo.UserControl
+{
+    public partial class AppNotification
+    {
+        public AppNotification()
+        {
+            InitializeComponent();
+        }
+    }
+}
+```
+
+```cs
+Notification.Show(new AppNotification(), ShowAnimation.Fade, true)
+```
+
+![Notification](https://raw.githubusercontent.com/HandyOrg/HandyOrgResource/master/HandyControl/Resources/Notification.png)