refactor: merge to Flexi UI and new usage

desktopApp/build.gradle.kts

@@ -24,6 +24,6 @@ java {
 
 compose.desktop {
     application {
-        mainClass = "MainKt"
+        mainClass = "$group.MainKt"
     }
 }

desktopApp/src/desktopMain/kotlin/Main.kt

@@ -1,3 +1,5 @@
+package __GROUP_NAME__
+
 import androidx.compose.ui.unit.dp
 import androidx.compose.ui.window.Window
 import androidx.compose.ui.window.application
@@ -8,5 +10,5 @@ fun main() = application {
         onCloseRequest = ::exitApplication,
         title = "__APP_NAME__",
         state = rememberWindowState(width = 550.dp, height = 450.dp)
-    ) { MainView() }
+    ) { App() }
 }