apiBaseUrl property Null safety

1. irte_engine
2. engine.config
3. EngineConfig
4. apiBaseUrl property

EngineConfig class

1. Constructors
2. EngineConfig
3. Properties
4. hashCode
5. runtimeType
6. Methods
7. noSuchMethod
8. toString
9. Operators
10. operator ==
11. Static properties
12. apiBaseUrl
13. authBaseUrl
14. name
15. speechPackageBaseUrl
16. Static methods
17. setUp
18. Constants
19. defaultLanguage