UploadManager constructor Null safety

1. baguette
2. UploadManager
3. UploadManager
4. UploadManager constructor

UploadManager class

1. Constructors
2. UploadManager
3. Properties
4. hashCode
5. runtimeType
6. Methods
7. addPlugin
8. cleanPlugins
9. getPlugin
10. noSuchMethod
11. removePlugin
12. toString
13. upload
14. Operators
15. operator ==