tab_scaffold library

modify from https://github.com/flutter/flutter/blob/master/packages/flutter/lib/src/cupertino/tab_scaffold.dart lastest push: 2019.12.29 flutter v1.13.5

lastest commit: 2019.12.17 commit https://github.com/flutter/flutter/commit/a82a39973369db5101d5cae9ae674a1f75fcd3eb #46106 https://github.com/flutter/flutter/pull/46106

Classes

CupertinoTabController
Coordinates tab selection between a CupertinoTabBar and a CupertinoTabScaffold. [...]
CupertinoTabScaffold
Implements a tabbed iOS application's root layout and behavior structure. [...]