Window.locale.

To access localized resources, use the Localizations.of() method
to access a specific localizations class that is provided by a given delegate.
Use the intl_translation package to extract translatable copy
to arb files for translating, and importing them back into the app
for using them with intl.

For further details on internationalization and localization in Flutter,
see the internationalization guide, which has sample code
with and without the intl package.

Where is my project file?

In Xamarin.Forms you will have a csproj file.
The closest equivalent in Flutter is pubspec.yaml,
which contains package dependencies and various project details.
Similar to .NET Standard,
files within the same directory are considered part of the project.

What is the equivalent of Nuget? How do I add dependencies?