make AppDelegate a bit swifty

Mini vMac/AppDelegate.h

@@ -23,8 +23,8 @@ extern NSString *DocumentsChangedNotification;
 @property (readonly, nonatomic, getter = isSandboxed) BOOL sandboxed;
 @property (readonly, nonatomic) id<Emulator> sharedEmulator;
 
-+ (instancetype)sharedInstance;
-+ (id<Emulator>)sharedEmulator;
+@property (class, readonly, strong) AppDelegate *sharedInstance NS_SWIFT_NAME(shared);
+@property (class, readonly, strong) id<Emulator> sharedEmulator NS_SWIFT_NAME(emulator);
 - (void)loadAndStartEmulator;
 
 - (void)showAlertWithTitle:(NSString *)title message:(NSString *)message;

Mini vMac/DefaultSceneDelegate.swift

@@ -15,7 +15,7 @@ class DefaultSceneDelegate: UIResponder, UIWindowSceneDelegate {
         guard let windowScene = scene as? UIWindowScene else {
             fatalError("Expected scene of type UIWindowScene but got an unexpected type")
         }
-        guard let appDelegate = AppDelegate.sharedInstance() else {
+        guard let appDelegate = AppDelegate.shared else {
             fatalError("No app delegate")
         }
 

Mini vMac/KeyboardSceneDelegate.swift

@@ -15,7 +15,7 @@ class KeyboardSceneDelegate: UIResponder, UIWindowSceneDelegate {
         guard let windowScene = scene as? UIWindowScene else {
             fatalError("Expected scene of type UIWindowScene but got an unexpected type")
         }
-        guard let mainViewController = AppDelegate.sharedInstance().window.rootViewController as? ViewController else {
+        guard let mainViewController = AppDelegate.shared.window.rootViewController as? ViewController else {
             fatalError("No main view controller")
         }
 

Mini vMac/VisionSupport.swift

@@ -21,13 +21,13 @@ extension ViewController {
                     Spacer(minLength: 80.0)
                     HStack {
                         Button(action: {
-                            AppDelegate.sharedInstance().showSettings(self)
+                            AppDelegate.shared.showSettings(self)
                         }, label: {
                             Image(systemName: "gear")
                         }).glassBackgroundEffect()
 
                         Button(action: {
-                            AppDelegate.sharedInstance().showInsertDisk(self)
+                            AppDelegate.shared.showInsertDisk(self)
                         }, label: {
                             Image(systemName: "opticaldiscdrive")
                         }).glassBackgroundEffect()
@@ -46,7 +46,7 @@ extension ViewController {
 
     @objc
     static func adjustToScreenSize() {
-        let screenSize = AppDelegate.sharedEmulator().screenSize
+        let screenSize = AppDelegate.emulator.screenSize
         guard let windowScene = UIApplication.shared.connectedScenes.first as? UIWindowScene else {
             return
         }