This PR contains the work done to define the `Coordinator` and the `Router` public protocols, and also implemented a few concrete router implementations tailored for the **UIKit** framework.
To provide further details about the work done:
- [x] define a new, dedicated `Coordinator` target in the `Package` file;
- [x] define the `Coordinator` and the `Router` public protocols used to implement the coordinator pattern;
- [x] implemented some **UIKit** specific routers to use on the **iOS** platform: `ModalNavigationRouter`, `PushNavigationRouter` and the `WindowRouter` concrete routers.
Co-authored-by: Javier Cicchelli <javier@rock-n-code.com>
Reviewed-on: #2