refactor(frontend): scripts -> utility

packages/frontend/src/utility/post-message.ts

@@ -0,0 +1,25 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+export const postMessageEventTypes = [
+	'misskey:shareForm:shareCompleted',
+] as const;
+
+export type PostMessageEventType = typeof postMessageEventTypes[number];
+
+export type MiPostMessageEvent = {
+	type: PostMessageEventType;
+	payload?: any;
+};
+
+/**
+ * 親フレームにイベントを送信
+ */
+export function postMessageToParentWindow(type: PostMessageEventType, payload?: any): void {
+	window.parent.postMessage({
+		type,
+		payload,
+	}, '*');
+}