ShortcutRegistry constructor Null safety

1. Flutter
2. widgets
3. ShortcutRegistry
4. ShortcutRegistry constructor

ShortcutRegistry class

1. Constructors
2. ShortcutRegistry
3. Properties
4. hashCode
5. hasListeners
6. runtimeType
7. shortcuts
8. Methods
9. addAll
10. addListener
11. dispose
12. noSuchMethod
13. notifyListeners
14. removeListener
15. toString
16. Operators
17. operator ==
18. Static methods
19. maybeOf
20. of