fix(rn,sidebar) fix not appearing on RTL languages

react/features/welcome/components/WelcomePageSideBar.native.js

         return (
             <SlidingView
                 onHide = { this._onHideSideBar }
-                position = 'left'
                 show = { this.props._visible }
                 style = { styles.sideBar } >
                 <Header style = { styles.sideBarHeader }>

react/features/welcome/components/styles.js

 // @flow
 
-import { StyleSheet } from 'react-native';
+import { Dimensions, StyleSheet } from 'react-native';
 
 import { BoxModel, ColorPalette } from '../../base/styles';
 
      * Container of the side bar.
      */
     sideBar: {
-        width: 250
+        width: 250,
+        height: Dimensions.get('window').height
     },
 
     /**