Adding support to return all audio types

src/app/api/tracks/route.ts

@@ -3,6 +3,12 @@ import { NextResponse } from 'next/server';
 
 const MUSIC_DIR = '/app/music';
 export async function GET() {
-  const files = fs.readdirSync(MUSIC_DIR).filter((f) => f.endsWith('.mp3'));
+  const files = fs
+    .readdirSync(MUSIC_DIR)
+    .filter((f) =>
+      ['.mp3', '.m4a', 'audio/mpeg', 'audio/mp4', 'audio/x-m4a'].some((suffix) =>
+        f.endsWith(suffix),
+      ),
+    );
   return NextResponse.json(files);
 }