Background constructor Null safety

1. cloudinary_url_gen
2. background
3. Background
4. Background constructor

Background class

1. Constructors
2. Background
3. Properties
4. hashCode
5. runtimeType
6. Methods
7. getValues
8. noSuchMethod
9. toString
10. Operators
11. operator ==
12. Static methods
13. auto
14. blurred
15. border
16. borderGradient
17. color
18. colorString
19. predominant
20. predominantGradient