V2 add additional ios options for tabbar icons (#3296)

* add option to disable tabbar icon tints and add custom selected icons

*  update docs for disabling tabbar icon tint and selectedIcon

* move new options to ios-specific section in docs

* delete trailing comma in docs

docs/docs/styling.md

     hideShadow: false
   },
   bottomTab: {
-    iconInsets: { top: 0, left: 0, bottom: 0, right: 0 }
+    iconInsets: { top: 0, left: 0, bottom: 0, right: 0 },
+    selectedIcon: require('selectedTab.png'),
+    disableIconTint: true, //set true if you want to disable the icon tinting
+    disableSelectedIconTint: true
   }
 }
 ```

lib/ios/RNNBottomTabOptions.h

 @property (nonatomic, strong) NSString* testID;
 @property (nonatomic, strong) NSNumber* visible;
 @property (nonatomic, strong) NSDictionary* icon;
+@property (nonatomic, strong) NSDictionary* selectedIcon;
+@property (nonatomic, strong) NSDictionary* disableIconTint;
+@property (nonatomic, strong) NSDictionary* disableSelectedIconTint;
 @property (nonatomic, strong) NSDictionary* iconInsets;
 
 @end

lib/ios/RNNBottomTabOptions.m

 
 - (void)applyOn:(UIViewController *)viewController {
 	if (self.title || self.icon) {
-		UITabBarItem* tabItem = [[UITabBarItem alloc] initWithTitle:self.title image:[RCTConvert UIImage:self.icon] tag:self.tag];
+		UIImage *iconImage = nil;
+		if (self.disableIconTint) {
+			iconImage = [[RCTConvert UIImage:self.icon] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal];
+		} else {
+			iconImage = [RCTConvert UIImage:self.icon];
+		}
+		UITabBarItem* tabItem = [[UITabBarItem alloc] initWithTitle:self.title image:iconImage tag:self.tag];
 		tabItem.accessibilityIdentifier = self.testID;
 		
 		if (self.iconInsets && ![self.iconInsets isKindOfClass:[NSNull class]]) {
 		
 		[viewController.navigationController setTabBarItem:tabItem];
 	}
+	if (self.selectedIcon) {
+		UIImage *selectedIconImage = nil;
+		if (self.disableSelectedIconTint) {
+			selectedIconImage = [[RCTConvert UIImage:self.selectedIcon] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal];
+		} else {
+			selectedIconImage = [RCTConvert UIImage:self.selectedIcon];
+		}
+		if (viewController.navigationController) {
+			viewController.navigationController.tabBarItem.selectedImage = selectedIconImage;
+		} else {
+			viewController.tabBarItem.selectedImage = selectedIconImage;
+		}	
+	}
 	
 	if (self.badge) {
 		NSString *badge = nil;