Add localisation support for strings

[bitigchi]

Checklist

• I've added at least one test that validates that my change is working, if appropriate
• I've followed the code style of the rest of the project
• I've read the Contribution Guidelines
• I've updated the documentation if necessary

[mpapple-swift]

Providing the ability to localize command line tools/apps is a great idea and I don't wish to dampen your enthusiasm for this effort. I do, however, wish to pose an open question for discussion: .lproj resources are unique to Apple/Darwin platforms - is this an appropriate design for a library that is cross-platform in nature? Of the leading (non-Swift) libraries I surveyed, none of them offers localization capabilities, so leveraging the Apple/Darwin approach is as good as any. But it is a fair question to ascertain if there are any reservations from developers on Linux or Windows? Otherwise, I'm +1 on adding this capability absent reservations about the design/implementation.

[bitigchi]

I personally think .lproj files are fine. There are already different approaches to this in other platforms, like how gettext handles stuff. However, it would be neat to have the framework automatically handle the localisations in bundle, like it does with regular AppKit/UIKit/SwiftUI apps, without having to manually locate .lproj files.