[Feature Request] Support user notification sounds on iOS

[ghost]

I've bought some nice (more relaxed) notification tones from iTunes on iOS. I would like to be able to use Telegram so when I choose a notification sound, the list of options include downloads/purchases and not just the default sounds.

If it's not possible, then maybe an option to use mp3s added manually by the user (instead of bought from iTunes)?

Telegram 5.0.15 on iOS 12.0.1