GlobalKey needed StatefulWidget

[chonghorizons]

Needed the MyWidget example for snap with key to be stateful widget. It was giving an error that currentState was not a method of key.

The docs for GlobalKey(https://api.flutter.dev/flutter/widgets/GlobalKey-class.html) says it only extends stateful widgets, i.e.

GlobalKey<T extends State<StatefulWidget>> class

Also, small typo of CamelCase on snapOnTap