completed extend-controls docs

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

@@ -0,0 +1,30 @@
+---
+title: SimpleText 简单文本
+---
+
+一种轻量级文本显示控件.
+
+```cs
+public class SimpleText : FrameworkElement
+```
+
+# 属性
+
+|属性|描述|默认值|备注|
+|-|-|-|-|
+|Text|文本|||
+|TextAlignment|文本对齐方式|TextAlignment.Left||
+|TextTrimming|文本截断方式|TextTrimming.None||
+|TextWrapping|文本换行方式|TextWrapping.NoWrap||
+|Foreground|字体颜色|||
+|FontFamily|字体|||
+|FontSize|字体大小|||
+|FontStretch|字体变形方式|||
+|FontStyle|字体风格|||
+|FontWeight|字体粗细||||
+
+# 案例
+
+```xml
+<hc:SimpleText Text="Content"/>
+```