New task feature (#2)

This PR contains the work done to implement the **New Task** feature, and to integrate it into the main context view of the app.

Reviewed-on: rock-n-code/todos-app#2
Co-authored-by: Javier Cicchelli <javier@rock-n-code.com>
Co-committed-by: Javier Cicchelli <javier@rock-n-code.com>

App/Sources/View Models/ContentViewModel.swift

@@ -0,0 +1,39 @@
+import SwiftData
+import SwiftUI
+
+extension ContentView {
+
+    /// View model for managing the logic for the content view.
+    ///
+    /// This observable class encapsulates the state and business logic for the main content view.
+    /// It follows the MVVM pattern to separate presentation logic from the view layer.
+    ///
+    /// The view model manages:
+    /// - Presentation state for the new task view within a sheet.
+    @Observable
+    class ViewModel {
+
+        // MARK: Properties
+
+        /// Whether the new task view should be shown.
+        var newTaskShown: Bool
+
+        // MARK: Initialization
+
+        /// Initializes a new view model instance with default values.
+        ///
+        /// The view model is initialized with:
+        /// - New task view hidden
+        init() {
+            newTaskShown = false
+        }
+
+        // MARK: Functions
+
+        /// Shows the new task view by setting the presentation state to true.
+        func showNewTask() {
+            newTaskShown = true
+        }
+
+    }
+}