1.  https://riverpod.dev/docs/introduction/getting_started
    1.1.  commands run in terminal
        >>
        flutter pub add flutter_riverpod
        flutter pub add riverpod_annotation
        flutter pub add dev:riverpod_generator
        flutter pub add dev:build_runner
        flutter pub add dev:custom_lint
        flutter pub add dev:riverpod_lint
        <<
    1.2.
       >>
       flutter pub get
       flutter pub run build_runner build ( instead of flutter pub run build_runner watch)
       <<
    1.3.  Add Links.txt file.