ICommander constructor Null safety

1. nyxx_commander
2. nyxx_commander
3. ICommander
4. ICommander constructor

ICommander class

1. Constructors
2. ICommander
3. Properties
4. commandEntities
5. hashCode
6. runtimeType
7. Methods
8. getPrefixForMessage
9. noSuchMethod
10. registerCommand
11. registerCommandEntity
12. registerCommandGroup
13. toString
14. Operators
15. operator ==
16. Static methods
17. create