Lmnt synthesizer

[parshvadaftari]

Description

LMNT TTS synthesizer into Vocode platform for the streaming and not turned-based.

• This commit finalizes the integration of the LMNT TTS synthesizer, enabling TTS capabilities for streaming conversations on the Vocode platform.
• Added LMNTSynthesizer class to handle speech synthesis using LMNT API in lmnt_synthesizer.py.
• Implemented create_speech_uncached and get_chunks methods for handling TTS requests and streaming audio.
• Updated LMNTSynthesizerConfig in lmnt_synthesizer_config.py to include necessary configurations such as api_key and voice_id.
• Modified streaming_conversation.py to utilize LMNT synthesizer for streaming conversations.
• Added default settings for openai_api_key, deepgram_api_key, and lmnt_api_key in Settings class.

Fixes #497 (Issue)

Type of hange

• New feature - LMNT

How Has This Been Tested?

• Unit tests

Maintainer Checklist

• closes LMNT as New Synthesizer #497 Issue
• Made sure Checks passed

Twiter Handle - Parshva - https://x.com/parshva_daftari

[parshvadaftari]

@arpagon @ajar98 Can you please review this PR??