Add Urdu (ur) G2P support to TTS pipeline

[mwzkhalil]

Feature Request: Urdu G2P for NeMo TTS

Motivation

Urdu is a widely spoken language (~230M speakers) with no current G2P support in NeMo.
Adding Urdu G2P would enable TTS model training and inference for Urdu text.

Urdu Script Notes

• Written in Nastaliq/Naskh Arabic script (RTL)
• Uses Urdu-specific characters (ے، ں، ڈ، ڑ، ھ etc.)
• IPA phoneme set exists for Urdu
• Resources available: eSpeakNG supports Urdu, open Urdu pronunciation dictionaries exist

Proposed Implementation

• Add UrduG2p class under nemo/collections/tts/g2p/
• Add Urdu phoneme set / IPA mapping
• Optionally: dictionary-based fallback using existing Urdu lexicons

I am willing to contribute a PR for this.

[pzelasko]

CC @blisc