trail property Null safety

1. baguette
2. TagWidget
3. TagWidget
4. trail property

TagWidget class

1. Constructors
2. TagWidget
3. Properties
4. backgroundColor
5. corner
6. foregroundColor
7. hashCode
8. highlight
9. highlightColor
10. key
11. label
12. lead
13. margin
14. onPress
15. padding
16. runtimeType
17. trail
18. Methods
19. createElement
20. createState
21. debugDescribeChildren
22. debugFillProperties
23. noSuchMethod
24. toDiagnosticsNode
25. toString
26. toStringDeep
27. toStringShallow
28. toStringShort
29. Operators
30. operator ==