add Gooey Effect Demo

src/Shared/HandyControlDemo_Shared/UserControl/Practical/Login.xaml

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+<UserControl x:Class="HandyControlDemo.UserControl.Login"
+             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="{DynamicResource RegionBrush}">
+    <Grid Width="320" Height="567" Background="#f2f3f7">
+        <StackPanel VerticalAlignment="Bottom">
+            <Button Content="ｻｲﾝｱｯプ" Height="44" Width="166" hc:BorderElement.CornerRadius="22" BorderThickness="0" Background="#41508d" Foreground="#edf0fb"/>
+        </StackPanel>
+    </Grid>
+</UserControl>

src/Shared/HandyControlDemo_Shared/UserControl/Practical/Login.xaml.cs

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+namespace HandyControlDemo.UserControl
+{
+    public partial class Login
+    {
+        public Login()
+        {
+            InitializeComponent();
+        }
+    }
+}