[Update] Add Window Title bar.

[bugfix] Note: I think this is tauri's bug. When I try to resize the window and hovered dragable area, I could see resize cursor but it work as a dragging the window behavior that should't be.
Updated npm packages but still not work so I  managed it as adding margin-top by referring Discord title bar.

src-tauri/src/main.rs

@@ -3,19 +3,26 @@
 
 // use tauri::command;
 use tauri::Manager;
+use window_shadows::set_shadow;
 fn main() {
     tauri::Builder::default()
         .setup(|app| {
+            let main_window = app.get_window("main").unwrap();  // `main_window` is declared here for all builds
+
             #[cfg(debug_assertions)]
-            app.get_window("main").unwrap().open_devtools(); // `main` is the first window from tauri.conf.json without an explicit label
+            { main_window.open_devtools(); }
+
+            #[cfg(any(windows, target_os = "macos"))]
+            set_shadow(main_window, true).unwrap();
+
             Ok(())
         })
         .invoke_handler(tauri::generate_handler![get_font_list])
         .run(tauri::generate_context!())
         .expect("error while running tauri application");
-
 }
 
+
 use font_kit::{source::SystemSource};
 use std::collections::HashSet;