outline property Null safety

1. Flutter
2. scheme
3. Scheme
4. outline property

Scheme class

1. Constructors
2. Scheme
3. Properties
4. background
5. error
6. errorContainer
7. hashCode
8. inverseOnSurface
9. inversePrimary
10. inverseSurface
11. onBackground
12. onError
13. onErrorContainer
14. onPrimary
15. onPrimaryContainer
16. onSecondary
17. onSecondaryContainer
18. onSurface
19. onSurfaceVariant
20. onTertiary
21. onTertiaryContainer
22. outline
23. primary
24. primaryContainer
25. runtimeType
26. secondary
27. secondaryContainer
28. shadow
29. surface
30. surfaceVariant
31. tertiary
32. tertiaryContainer
33. Methods
34. noSuchMethod
35. toString
36. Operators
37. operator ==
38. Static methods
39. dark
40. darkFromCorePalette
41. light
42. lightFromCorePalette