[macos] Feature to set labeled badge on taskbar aka dock

lib/src/window_manager.dart

@@ -544,6 +544,19 @@ class WindowManager {
     await _channel.invokeMethod('setIcon', arguments);
   }
 
+  /// Set/unset label on taskbar(dock) app icon
+  ///
+  /// Note that it's required to request access at your AppDelegate.swift like this:
+  /// UNUserNotificationCenter.current().requestAuthorization(options: [.alert, .badge]) <...>
+  ///                                                                           ^---
+  /// @platforms macos
+  Future<void> setBadgeLabel([String? label]) async {
+    final Map<String, dynamic> arguments = {
+      'label': label ?? '',
+    };
+    await _channel.invokeMethod('setBadgeLabel', arguments);
+  }
+
   /// Returns `bool` - Whether the window has a shadow. On Windows, always returns true unless window is frameless.
   ///
   /// @platforms macos,windows

macos/Classes/WindowManager.swift

@@ -370,6 +370,11 @@ public class WindowManager: NSObject, NSWindowDelegate {
         let isSkipTaskbar: Bool = args["isSkipTaskbar"] as! Bool
         NSApplication.shared.setActivationPolicy(isSkipTaskbar ? .accessory : .regular)
     }
+
+    public func setBadgeLabel(_ args: [String: Any]) {
+        let label: String = args["label"] as! String
+        NSApplication.shared.dockTile.badgeLabel = label
+    }
 
     public func setProgressBar(_ args: [String: Any]) {
         let progress: CGFloat = CGFloat(truncating: args["progress"] as! NSNumber)

macos/Classes/WindowManagerPlugin.swift

@@ -208,6 +208,10 @@ public class WindowManagerPlugin: NSObject, FlutterPlugin {
             windowManager.setSkipTaskbar(args)
             result(true)
             break
+        case "setBadgeLabel":
+            windowManager.setBadgeLabel(args)
+            result(true)
+            break
         case "setProgressBar":
             windowManager.setProgressBar(args)
             result(true)