layout direction docs (#4810)

docs/docs/styling.md

@@ -64,6 +64,7 @@ Navigation.mergeOptions(this.props.componentId, {
     style: 'light' | 'dark'
   },
   layout: {
+    direction: 'ltr', // Supported directions are: 'rtl', 'ltr'
     backgroundColor: 'white',
     orientation: ['portrait', 'landscape'] // An array of supported orientations
   },
@@ -253,6 +254,26 @@ Navigation.mergeOptions(this.props.componentId, {
 }
 ```
 
+### RTL layout usage
+In order to set layout direction to RTL use following options:
+```javascript
+{
+  layout: {
+    direction: rtl
+  },
+  ...
+}
+```
+
+also __Android__ requires to set `supportsRTL` in _AndroidManifest.xml_
+```xml
+<application
+      android:name=".MainApplication"
++     android:supportsRtl="true"
+      ...
+      android:theme="@style/AppTheme">
+```
+
 ## Styling the StatusBar
 If you set any styles related to the Status Bar, make sure that in Xcode > project > Info.plist, the property `View controller-based status bar appearance` is set to `YES`.