added drawUnder (#2427)

lib/ios/RNNTabBarOptions.m

 	self.currentTabIndex = [tabBarOptions valueForKey:@"currentTabIndex"];
 	self.testID = [tabBarOptions valueForKey:@"testID"];
 	self.currentTabId = [tabBarOptions valueForKey:@"currentTabId"];
+	self.drawUnder = [tabBarOptions valueForKey:@"drawUnder"];
 	
 	return self;
 }

lib/ios/RNNTopBarOptions.m

 	self.animateHide = [topBarOptions valueForKey:@"animateHide"];
 	self.largeTitle = [topBarOptions valueForKey:@"largeTitle"];
 	self.testID = [topBarOptions valueForKey:@"testID"];
+	self.drawUnder = [topBarOptions valueForKey:@"drawUnder"];
 	
 	return self;
 }

lib/src/params/options/BottomTabs.js

    * @property {boolean} [hidden]
    * @property {boolean} [animateHide]
    * @property {string} [testID]
+   * @property {boolean} [drawUnder]
    */
   constructor(params) {
     if (isEmpty(params)) {
     this.hidden = params.hidden;
     this.animateHide = params.animateHide;
     this.testID = params.testID;
+    this.drawUnder = params.drawUnder;
   }
 }
 

lib/src/params/options/TopBar.js

    * @property {boolean} [blur]
    * @property {boolean} [noBorder]
    * @property {boolean} [largeTitle]
+   * @property {boolean} [drawUnder]
    */
   constructor(options) {
     this.title = options.title;
     this.noBorder = options.noBorder;
     this.largeTitle = options.largeTitle;
     this.testID = options.testID;
+    this.drawUnder = options.drawUnder;
   }
 }