Show app startup screen by default (#5036)

* initial commit

* pubspec.lock

* py: `show_app_startup_screen` defaults to `True`

* revert to false

* set showAppStartupScreen=true in client

Author: ndonkoHenri

client/lib/main.dart

@@ -103,6 +103,7 @@ void main([List<String>? args]) async {
     pageUrl: pageUrl,
     assetsDir: assetsDir,
     errorsHandler: errorsHandler,
+    showAppStartupScreen: true,
     createControlFactories: [
 // --FAT_CLIENT_START--
       flet_audio.createControl,

client/pubspec.lock

@@ -263,7 +263,7 @@ packages:
       path: "../packages/flet"
       relative: true
     source: path
-    version: "0.27.1"
+    version: "0.27.5"
   flet_ads:
     dependency: "direct main"
     description: