Basic application setup (#1)

This PR contains the work done to define the necessary setup from which the app will be built upon.

To provide further details on what has been done:
* created the app, the unit tests and the UI tests targets in the Xcode project;
* updated the bundle identifiers and OS deployment targets of all targets;
* added a `.gitignore` file tailored specifically for the project;
* added a `README` file that defines in details the goal of the project;
* added the [Swift Format](https://github.com/swiftlang/swift-format) rules that the source code should abide to;
* cleaned the boilerplate source code on all targets.

Reviewed-on: rock-n-code/todos-app#1
Co-authored-by: Javier Cicchelli <javier@rock-n-code.com>
Co-committed-by: Javier Cicchelli <javier@rock-n-code.com>

App/Sources/App/TodosApp.swift

@@ -0,0 +1,26 @@
+import SwiftData
+import SwiftUI
+
+@main
+struct TodosApp: App {
+    var sharedModelContainer: ModelContainer = {
+        let schema = Schema([
+            Item.self
+        ])
+        let modelConfiguration = ModelConfiguration(schema: schema, isStoredInMemoryOnly: false)
+
+        do {
+            return try ModelContainer(for: schema, configurations: [modelConfiguration])
+        }
+        catch {
+            fatalError("Could not create ModelContainer: \(error)")
+        }
+    }()
+
+    var body: some Scene {
+        WindowGroup {
+            ContentView()
+        }
+        .modelContainer(sharedModelContainer)
+    }
+}

App/Sources/Models/Item.swift

@@ -0,0 +1,11 @@
+import Foundation
+import SwiftData
+
+@Model
+final class Item {
+    var timestamp: Date
+
+    init(timestamp: Date) {
+        self.timestamp = timestamp
+    }
+}

App/Sources/Views/ContentView.swift

@@ -0,0 +1,63 @@
+import SwiftData
+import SwiftUI
+
+struct ContentView: View {
+
+    @Environment(\.modelContext)
+    private var modelContext
+
+    @Query
+    private var items: [Item]
+
+    var body: some View {
+        NavigationSplitView {
+            List {
+                ForEach(items) { item in
+                    NavigationLink {
+                        Text("Item at \(item.timestamp, format: Date.FormatStyle(date: .numeric, time: .standard))")
+                    } label: {
+                        Text(item.timestamp, format: Date.FormatStyle(date: .numeric, time: .standard))
+                    }
+                }
+                .onDelete(perform: deleteItems)
+            }
+            #if os(macOS)
+            .navigationSplitViewColumnWidth(min: 180, ideal: 200)
+            #endif
+            .toolbar {
+                #if os(iOS)
+                ToolbarItem(placement: .navigationBarTrailing) {
+                    EditButton()
+                }
+                #endif
+                ToolbarItem {
+                    Button(action: addItem) {
+                        Label("Add Item", systemImage: "plus")
+                    }
+                }
+            }
+        } detail: {
+            Text("Select an item")
+        }
+    }
+
+    private func addItem() {
+        withAnimation {
+            let newItem = Item(timestamp: Date())
+            modelContext.insert(newItem)
+        }
+    }
+
+    private func deleteItems(offsets: IndexSet) {
+        withAnimation {
+            for index in offsets {
+                modelContext.delete(items[index])
+            }
+        }
+    }
+}
+
+#Preview {
+    ContentView()
+        .modelContainer(for: Item.self, inMemory: true)
+}