Coding constructor Null safety

1. conduit_codable
2. conduit_codable
3. Coding
4. Coding constructor

Coding class

1. Constructors
2. Coding
3. Properties
4. castMap
5. hashCode
6. referenceURI
7. runtimeType
8. Methods
9. decode
10. encode
11. noSuchMethod
12. toString
13. Operators
14. operator ==