feat(mobile/navigation): added screen orientation based on Platform

react/features/mobile/navigation/screenOptions.js

 import React from 'react';
+import { Platform } from 'react-native';
 
 import {
     Icon,
     headerShown: true,
     headerStyle: {
         backgroundColor: BaseTheme.palette.screen02Header
-    }
+    },
+    orientation: Platform.select({
+        ios: 'default',
+        android: 'all'
+    })
 };
 
 /**
 export const conferenceScreenOptions = {
     animation: 'default',
     gestureEnabled: false,
-    headerShown: false
+    headerShown: false,
+    orientation: Platform.select({
+        ios: 'default',
+        android: 'all'
+    })
 };
 
 /**
     },
     headerTitleStyle: {
         color: BaseTheme.palette.text01
-    }
+    },
+    orientation: Platform.select({
+        ios: 'default',
+        android: 'all'
+    })
 };
 
 /**
     },
     headerTitleStyle: {
         color: BaseTheme.palette.text01
-    }
+    },
+    orientation: Platform.select({
+        ios: 'default',
+        android: 'all'
+    })
 };