Fix invoke calls in dialog & shell init scripts (#675)

Co-authored-by: Lucas Nogueira <lucas@tauri.studio>

plugins/dialog/guest-js/init.ts

@@ -0,0 +1,18 @@
+// Copyright 2019-2023 Tauri Programme within The Commons Conservancy
+// SPDX-License-Identifier: Apache-2.0
+// SPDX-License-Identifier: MIT
+
+import { invoke } from "@tauri-apps/api/primitives";
+
+window.alert = function (message: string) {
+  invoke("plugin:dialog|message", {
+    message: message.toString(),
+  });
+};
+
+// @ts-expect-error tauri does not have sync IPC :(
+window.confirm = function (message: string) {
+  return invoke("plugin:dialog|confirm", {
+    message: message.toString(),
+  });
+};