enhance(frontend): Shareページでの投稿完了時にpostMessageを発火するように (#12505)

* enhance(frontend): Shareページでの投稿完了時にpostMessageを発火

* Update Changelog

* fix

* 名前の混同をさける

* 名前をわかりやすくする

* watchを使わずパフォーマンス改善

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

@@ -0,0 +1,25 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and other misskey contributors
+ * 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.postMessage({
+		type,
+		payload,
+	}, '*');
+}