[fix] StyleSheet: add hairlineWidth

Fix #99

docs/apis/StyleSheet.md

@@ -11,6 +11,12 @@ outside of the render loop and are applied as inline styles. Read more about to
 
 Each key of the object passed to `create` must define a style object.
 
+## Properties
+
+**hairlineWidth**: number
+
+**flatten**: function
+
 ## Example
 
 ```js

src/apis/StyleSheet/index.js

@@ -70,6 +70,7 @@ module.exports = {
   _renderToString,
   create,
   elementId: ELEMENT_ID,
+  hairlineWidth: 1,
   flatten: flattenStyle,
   resolve
 }