Add macos icons

Use a fork of flutter_launcher_icons as the original hasn't responded to the
PR for macos icons.

pubspec.lock

@@ -512,9 +512,11 @@ packages:
   flutter_launcher_icons:
     dependency: "direct dev"
     description:
-      name: flutter_launcher_icons
-      url: "https://pub.dartlang.org"
-    source: hosted
+      path: "."
+      ref: HEAD
+      resolved-ref: "822002172c1d2aa05d3ee7f2ac179d2980980a3c"
+      url: "https://github.com/dirkbo/flutter_launcher_icons"
+    source: git
     version: "0.9.0"
   flutter_localizations:
     dependency: "direct main"

pubspec.yaml

@@ -89,7 +89,8 @@ dev_dependencies:
     sdk: flutter
   benchmark_harness: ^2.0.0
   bonsoir: ^1.0.0
-  flutter_launcher_icons: ^0.9.0
+  flutter_launcher_icons:
+    git: https://github.com/dirkbo/flutter_launcher_icons
   # flutter_webview_plugin: ^0.3.11
   import_sorter: ^4.4.3
   multicast_dns: ^0.3.0
@@ -120,6 +121,9 @@ flutter_icons:
   image_path: "assets/icon/icon.png"
   image_path_ios: "assets/icon/icon_ios.png"
   ios: true
+  macos: true
+  windows: false
+  linux: false
 
 import_sorter:
   comments: false