feat(macos): add Swift Package Manager support

Closes #98

Adds Package.swift at macos/tray_manager/Package.swift so Flutter 3.24+ can build this plugin via SPM. Sources are moved from macos/Classes/ to macos/tray_manager/Classes/ so SPM can reference them. CocoaPods builds are unaffected.

Author: lijy91

.gitignore

@@ -4,3 +4,4 @@
 *.iml
 pubspec_overrides.yaml
 pubspec.lock
+**/macos/.build/

packages/tray_manager/macos/tray_manager.podspec

@@ -13,7 +13,7 @@ A new flutter plugin project.
   s.license          = { :file => '../LICENSE' }
   s.author           = { 'Your Company' => 'email@example.com' }
   s.source           = { :path => '.' }
-  s.source_files     = 'Classes/**/*'
+  s.source_files     = 'tray_manager/Classes/**/*'
   s.dependency 'FlutterMacOS'
 
   s.platform = :osx, '10.11'

…ray_manager/macos/Classes/TrayIcon.swift …acos/tray_manager/Classes/TrayIcon.swiftpackages/tray_manager/macos/Classes/TrayIcon.swift renamed to packages/tray_manager/macos/tray_manager/Classes/TrayIcon.swift packages/tray_manager/macos/Classes/TrayIcon.swift renamed to packages/tray_manager/macos/tray_manager/Classes/TrayIcon.swift

@@ -5,6 +5,8 @@
 //  Created by Lijy91 on 2022/5/15.
 //
 
+import AppKit
+
 public class TrayIcon: NSView {
     public var onTrayIconMouseDown:(() -> Void)?
     public var onTrayIconMouseUp:(() -> Void)?

…er/macos/Classes/TrayManagerPlugin.swift …_manager/Classes/TrayManagerPlugin.swiftpackages/tray_manager/macos/Classes/TrayManagerPlugin.swift renamed to packages/tray_manager/macos/tray_manager/Classes/TrayManagerPlugin.swift packages/tray_manager/macos/Classes/TrayManagerPlugin.swift renamed to packages/tray_manager/macos/tray_manager/Classes/TrayManagerPlugin.swift

@@ -0,0 +1,22 @@
+// swift-tools-version: 5.9
+// The swift-tools-version declares the minimum version of Swift required to build this package.
+
+import PackageDescription
+
+let package = Package(
+    name: "tray_manager",
+    platforms: [
+        .macOS("10.14")
+    ],
+    products: [
+        .library(name: "tray-manager", targets: ["tray_manager"])
+    ],
+    dependencies: [],
+    targets: [
+        .target(
+            name: "tray_manager",
+            dependencies: [],
+            path: "Classes"
+        )
+    ]
+)