widgets/plan_selection_dialog library

1. billing_feature package
2. documentation
3. widgets/plan_selection_dialog.dart

billing_feature package

1. Libraries
2. billing
3. billing_feature
4. billing_feature_method_channel
5. billing_feature_platform_interface
6. billing_feature_web
7. config/billing_feature_config
8. l10n/billing_localizations
9. l10n/billing_localizations_en
10. l10n/l10n
11. widgets/plan_selection_dialog