Update styling.md

docs/docs/styling.md

     badge: '2',
     testID: 'bottomTabTestID',
     visible: undefined,
-    icon: require('tab.png')
+    icon: require('tab.png'),
+    iconInsets: { top: 0, left: 0, bottom: 0, right: 0 }
   },
   sideMenu: {
     left: {