added: infinite_list example to readme index
added: infinite_list example to readme index

nisrulz/flutter-examples,nisrulz/flutter-examples,nisrulz/flutter-examples,nisrulz/flutter-examples,nisrulz/flutter-examples,nisrulz/flutter-examples,nisrulz/flutter-examples,nisrulz/flutter-examples,nisrulz/flutter-examples