feat: migration to TypeScript part 2

Co-authored-by: Su-Yong <simssy2205@gmail.com>

plugins/crossfade/back.ts

@@ -0,0 +1,15 @@
+import { ipcMain } from 'electron';
+import { Innertube } from 'youtubei.js';
+
+import config from './config';
+
+export default async () => {
+  const yt = await Innertube.create();
+
+  ipcMain.handle('audio-url', async (_, videoID: string) => {
+    const info = await yt.getBasicInfo(videoID);
+    const url = info.streaming_data?.formats[0].decipher(yt.session.player);
+
+    return url;
+  });
+};