Application localization should be inferred

[alvaromb]

App should infer as many settings as possible, using the user configured localization instead of making the user to choose the language. Also, using exit(0); has been considered against best practices in iOS, as per Apple's QA1561 Technical Q&A. Using standard localization strings is also being used in similar contact tracing apps, like Swiss Covid.

Is the team open to the following changes?

1. Infer user's language in language selector of WelcomeViewController.swift.
2. Use a more standard localization approach.

[iCesofT]

We get localisation strings from a service (see configuration server and Contentful), so we can change a text without upgrading the application. Also we can share strings between platforms (iOS / Android).