Finish MacOS and Windows version (won't commit if linux is fine)

src-tauri/src/lib.rs

@@ -158,6 +158,12 @@ fn load(app: AppHandle, name: String) {
 #[cfg_attr(mobile, tauri::mobile_entry_point)]
 pub fn run() {
     tauri::Builder::default()
+        .plugin(tauri_plugin_single_instance::init(|app, _args, _cwd| {
+            let _ = app
+                .get_webview_window("main")
+                .expect("no main window")
+                .set_focus();
+        }))
         .plugin(tauri_plugin_dialog::init())
         .plugin(tauri_plugin_opener::init())
         .plugin(tauri_plugin_os::init())