sort_button_view library Null safety

1. soreo
2. sort_button_view library

soreo package

1. Libraries
2. app_bar_view
3. authentication_bloc
4. authentication_repository
5. authentication_status
6. loading_page
7. main
8. post
9. post_bloc
10. post_list_page
11. post_list_view
12. post_page
13. post_repository
14. post_view
15. reddit_client
16. search_page
17. settings
18. sort_button_view
19. subreddit
20. subreddit_bloc
21. subreddit_page
22. subreddit_view
23. subscribe_button_view
24. user
25. user_icon_page
26. user_icon_view
27. user_profile_page
28. user_profile_view
29. user_repository
30. video_view