[iOS] Different Tabbar item text colors (#1276)

Added different tabbar label colors

docs/styling-the-tab-bar.md

   tabBarBackgroundColor: '#551A8B' // change the background color of the tab bar
   tabBarTranslucent: false // change the translucent of the tab bar to false
   tabBarTextFontFamily: 'Avenir-Medium' //change the tab font family
+  tabBarLabelColor: '#ffb700', // iOS only. change the color of tab text
+  tabBarSelectedLabelColor: 'red', // iOS only. change the color of the selected tab text
+  forceTitlesDisplay: true // Android only. If true - Show all bottom tab labels. If false - only the selected tab's label is visible.
   tabBarHideShadow: true // iOS only. Remove default tab bar top shadow (hairline)
   forceTitlesDisplay: true // Android only. If true - Show all bottom tab labels. If false - only the selected tab's label is visible.
 }

ios/RCCTabBarController.m

   
   UIColor *buttonColor = nil;
   UIColor *selectedButtonColor = nil;
+  UIColor *labelColor = nil;
+  UIColor *selectedLabelColor = nil;
   NSDictionary *tabsStyle = props[@"style"];
   if (tabsStyle)
   {
       buttonColor = color;
       selectedButtonColor = color;
     }
-    
     NSString *tabBarSelectedButtonColor = tabsStyle[@"tabBarSelectedButtonColor"];
     if (tabBarSelectedButtonColor)
     {
       self.tabBar.tintColor = color;
       selectedButtonColor = color;
     }
-    
+    NSString *tabBarLabelColor = tabsStyle[@"tabBarLabelColor"];
+    if(tabBarLabelColor) {
+      UIColor *color = tabBarLabelColor != (id)[NSNull null] ? [RCTConvert UIColor:tabBarLabelColor] : nil;
+      labelColor = color;
+    }
+    NSString *tabBarSelectedLabelColor = tabsStyle[@"tabBarSelectedLabelColor"];
+    if(tabBarLabelColor) {
+      UIColor *color = tabBarSelectedLabelColor != (id)[NSNull null] ? [RCTConvert UIColor:
+                                                                        tabBarSelectedLabelColor] : nil;
+      selectedLabelColor = color;
+    }
     NSString *tabBarBackgroundColor = tabsStyle[@"tabBarBackgroundColor"];
     if (tabBarBackgroundColor)
     {
       
       viewController.tabBarItem.imageInsets = UIEdgeInsetsMake(top, left, bottom, right);
     }
-    
     NSMutableDictionary *unselectedAttributes = [RCTHelpers textAttributesFromDictionary:tabsStyle withPrefix:@"tabBarText" baseFont:[UIFont systemFontOfSize:10]];
-    if (!unselectedAttributes[NSForegroundColorAttributeName] && buttonColor) {
-      unselectedAttributes[NSForegroundColorAttributeName] = buttonColor;
+    if (!unselectedAttributes[NSForegroundColorAttributeName] && labelColor) {
+      unselectedAttributes[NSForegroundColorAttributeName] = labelColor;
     }
     
-    [viewController.tabBarItem setTitleTextAttributes:unselectedAttributes forState:UIControlStateNormal]
-    ;
+    [viewController.tabBarItem setTitleTextAttributes:unselectedAttributes forState:UIControlStateNormal];
     
     NSMutableDictionary *selectedAttributes = [RCTHelpers textAttributesFromDictionary:tabsStyle withPrefix:@"tabBarSelectedText" baseFont:[UIFont systemFontOfSize:10]];
-    if (!selectedAttributes[NSForegroundColorAttributeName] && selectedButtonColor) {
-      selectedAttributes[NSForegroundColorAttributeName] = selectedButtonColor;
+    if (!selectedAttributes[NSForegroundColorAttributeName] && selectedLabelColor) {
+      selectedAttributes[NSForegroundColorAttributeName] = selectedLabelColor;
     }
     
     [viewController.tabBarItem setTitleTextAttributes:selectedAttributes forState:UIControlStateSelected];