[Feature]: add text-to-singing 🎤🎵

[funmolde]

Hello 😀,
I'd like to suggest adding a text-to-singing voice synthesis feature.
https://github.com/topics/singing-voice-synthesis
Thank you -_-

[JackismyShephard]

@funmolde What would the use case be here? Just generate a vocals track based on lyrics? That might be interesting. Applio already has a TTS-RVC feature which maybe can be extended for this use case. It might be something I will implement later.