NERoomChatCustomMessage constructor Null safety

1. netease_roomkit
2. netease_roomkit
3. NERoomChatCustomMessage
4. NERoomChatCustomMessage constructor

NERoomChatCustomMessage class

1. Constructors
2. NERoomChatCustomMessage
3. Properties
4. attachStr
5. fromNick
6. fromUserUuid
7. hashCode
8. message
9. messageType
10. messageUuid
11. of
12. runtimeType
13. time
14. toUserUuidList
15. Methods
16. noSuchMethod
17. toString
18. Operators
19. operator *
20. operator ==