sports property Null safety

1. equizz
2. player_database_stats
3. CategoryInformation
4. sports property

CategoryInformation class

1. Constructors
2. CategoryInformation
3. fromJson
4. Properties
5. art
6. entertainment
7. generalKnowledge
8. hashCode
9. history
10. mythology
11. runtimeType
12. science
13. sports
14. Methods
15. getAttributes
16. getCategoryName
17. noSuchMethod
18. toJson
19. toString
20. Operators
21. operator ==