add Loading doc

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

@@ -1,5 +1,54 @@
 ---
-title: 建设中
+title: Loading 加载条
 ---
 
-建设中
+耗时操作时显示动效，目前包含圆形和直线两种加载条。相关博文：[《WPF 控件库——仿制Windows10的进度条》](https://www.cnblogs.com/nabian/p/9288576.html)
+
+```cs
+public abstract class LoadingBase : ContentControl
+```
+
+```cs
+public class LoadingLine : LoadingBase
+```
+
+```cs
+public class LoadingCircle : LoadingBase
+```
+
+# LoadingBase 属性
+
+|属性|描述|默认值|备注|
+|-|-|-|-|
+|IsRunning|是否处于加载|true||
+|DotCount|圆点数目|5||
+|DotInterval|圆点间隙|10||
+|DotBorderBrush|圆点边框颜色|||
+|DotBorderThickness|圆点边框粗细|0||
+|DotDiameter|圆点半径|6||
+|DotSpeed|一遍循环所用时间|4s||
+|DotDelayTime|各点的动画延迟|80ms|||
+
+# LoadingCircle 属性
+
+|属性|描述|默认值|备注|
+|-|-|-|-|
+|DotOffSet|圆点偏移|20||
+|NeedHidden|圆点运动中途是否需要隐藏|true|||
+
+# 案例
+
+```xml
+<StackPanel Width="600" Margin="32" VerticalAlignment="Center">
+    <hc:LoadingLine/>
+    <hc:LoadingLine Margin="0,30" Foreground="BlueViolet" Style="{StaticResource LoadingLineLarge}"/>
+    <StackPanel Orientation="Horizontal" HorizontalAlignment="Center">
+        <hc:LoadingCircle/>
+        <Border VerticalAlignment="Center" Margin="32,0,0,0" Background="{DynamicResource PrimaryBrush}" CornerRadius="10">
+            <hc:LoadingCircle Style="{StaticResource LoadingCircleLight}" Margin="10"/>
+        </Border>
+    </StackPanel>
+</StackPanel>
+```
+
+![Loading](https://raw.githubusercontent.com/HandyOrg/HandyOrgResource/master/HandyControl/Resources/Loading.gif)