focusElevation property Null safety

1. flutter_json_widgets
2. widget
3. FloatingActionButtonExtended
4. focusElevation property

FloatingActionButtonExtended class

1. Constructors
2. FloatingActionButtonExtended
3. fromJson
4. Properties
5. autofocus
6. backgroundColor
7. clipBehavior
8. copyWith
9. disabledElevation
10. elevation
11. enableFeedback
12. focusColor
13. focusElevation
14. foregroundColor
15. hashCode
16. highlightElevation
17. hoverColor
18. hoverElevation
19. icon
20. isExtended
21. key
22. label
23. materialTapTargetSize
24. mouseCursor
25. onPressed
26. runtimeType
27. shape
28. splashColor
29. tooltip
30. Methods
31. map
32. mapOrNull
33. maybeMap
34. maybeWhen
35. noSuchMethod
36. toJson
37. toString
38. when
39. whenOrNull
40. Operators
41. operator ==