strings property Null safety

1. flutter_cast_framework
2. cast
3. MediaMetadata
4. strings property

MediaMetadata class

1. Constructors
2. MediaMetadata
3. Properties
4. hashCode
5. mediaType
6. runtimeType
7. strings
8. webImages
9. Methods
10. encode
11. noSuchMethod
12. toString
13. Operators
14. operator ==
15. Static methods
16. decode