[Feature] Dependencies (#3)

This PR contains the work done to provide a simple dependency injection feature whenever required.

To provide further details about this work:
- [x] renamed the `Coordinator` target in the `Package` file as `Coordination`;
- [x] declared the `Dependencies` target in the `Package` file;
- [x] defined the `DependencyKey` public protocol;
- [x] implemented the `DependencyService` public service;
- [x] implemented the `Dependency` public property wrapper;

Co-authored-by: Javier Cicchelli <javier@rock-n-code.com>
Reviewed-on: #3

Tests/Coordination/Platform/iOS/Helpers/TestCoordinators.swift

@@ -0,0 +1,106 @@
+//
+//  TestCoordinators.swift
+//  CoordinationTests
+//
+//  Created by Javier Cicchelli on 11/04/2023.
+//  Copyright © 2023 Röck+Cöde. All rights reserved.
+//
+
+import Coordination
+import UIKit
+
+// MARK: - Test coordinators
+
+class SomeCoordinator: Coordinator {
+    
+    // MARK: Properties
+    
+    var children: [Coordinator] = []
+    var router: Router
+    
+    // MARK: Initialisers
+    
+    init(router: Router) {
+        self.router = router
+    }
+    
+    // MARK: Functions
+    
+    func present(animated: Bool, onDismiss: (() -> Void)?) {
+        router.present(
+            SomeViewController(),
+            animated: animated,
+            onDismiss: onDismiss
+        )
+    }
+
+}
+
+class SomeOtherCoordinator: Coordinator {
+
+    // MARK: Properties
+    
+    var children: [Coordinator] = []
+    var router: Router
+    
+    // MARK: Initialisers
+    
+    init(router: Router) {
+        self.router = router
+    }
+    
+    // MARK: Functions
+    
+    func present(animated: Bool, onDismiss: (() -> Void)?) {
+        router.present(
+            SomeOtherViewController(),
+            animated: animated,
+            onDismiss: onDismiss
+        )
+    }
+
+}
+
+// MARK: - SpyRouter
+
+class SpyRouter: Router {
+    
+    // MARK: Enumerations
+    
+    enum State {
+        case initialised
+        case presented
+        case dismissed
+    }
+    
+    // MARK: Properties
+    
+    var state: State = .initialised
+    var viewController: UIViewController?
+    var animated: Bool?
+    var onDismiss: OnDismissedClosure?
+    
+    // MARK: Functions
+    
+    func present(
+        _ viewController: UIViewController,
+        animated: Bool,
+        onDismiss: OnDismissedClosure?
+    ) {
+        self.viewController = viewController
+        self.animated = animated
+        self.onDismiss = onDismiss
+        self.state = .presented
+    }
+    
+    func dismiss(animated: Bool) {
+        self.animated = animated
+        self.state = .dismissed
+    }
+    
+}
+
+// MARK: - Test view controllers
+
+class SomeViewController: UIViewController {}
+class SomeOtherViewController: UIViewController {}