recording_fields/dropdown library

1. self_test package
2. documentation
3. recording_fields/dropdown.dart

self_test package

1. Libraries
2. annotations
3. recording_fields/button
4. recording_fields/checkbox
5. recording_fields/dropdown
6. recording_fields/floating_action_button
7. recording_fields/list_tile
8. recording_fields/radio
9. recording_fields/slider
10. recording_fields/switch
11. recording_fields/text_field
12. recording_fields/text_form_field
13. self_test