margin property Null safety

1. baguette
2. TextWidget
3. TextWidget
4. margin property

TextWidget class

1. Constructors
2. TextWidget
3. Properties
4. hashCode
5. height
6. key
7. margin
8. over
9. padding
10. runtimeType
11. text
12. under
13. width
14. Methods
15. build
16. createElement
17. debugDescribeChildren
18. debugFillProperties
19. noSuchMethod
20. toDiagnosticsNode
21. toString
22. toStringDeep
23. toStringShallow
24. toStringShort
25. Operators
26. operator ==