[Feature request] Add Finetuning to XTTS Model

[muhi-zatar]

🚀 Feature Description

Excited for XTTS output for Arabic language since it is the first Arabic TTS released by Coqui TTS. However it does not offer fine-tuning or further training, which we could use to enhance the Arabic pronunciation with diacratization.

Thank you

[adhikjoshi]

Training script to add new languages +++

[erogol]

@muhi-zatar if you point out what we should do for diacratization, we can try internally.

[Edresson]

XTTS GPT training code will be available soon. You can see the progress on the PR #3086

[Edresson]

It was already added in the latest 🐸 TTS version: https://tts.readthedocs.io/en/dev/models/xtts.html#training