CommandExtension constructor Null safety

1. Flutter
2. flutter_driver_extension
3. CommandExtension
4. CommandExtension constructor

CommandExtension class

1. Constructors
2. CommandExtension
3. Properties
4. commandKind
5. hashCode
6. runtimeType
7. Methods
8. call
9. deserialize
10. noSuchMethod
11. toString
12. Operators
13. operator ==