Add Soniox real-time TTS service

Introduce SonioxTTSService, a WebSocket TTS provider that streams text and
receives audio over a persistent connection, multiplexing up to 5 concurrent
streams per socket via Soniox's `stream_id`. Also updates the README service
table and the Soniox voice example to use the new TTS end-to-end.

examples/voice/voice-soniox.py

@@ -22,9 +22,9 @@ from pipecat.processors.aggregators.llm_response_universal import (
 )
 from pipecat.runner.types import RunnerArguments
 from pipecat.runner.utils import create_transport
-from pipecat.services.cartesia.tts import CartesiaTTSService
 from pipecat.services.openai.llm import OpenAILLMService
 from pipecat.services.soniox.stt import SonioxSTTService
+from pipecat.services.soniox.tts import SonioxTTSService
 from pipecat.transcriptions.language import Language
 from pipecat.transports.base_transport import BaseTransport, TransportParams
 from pipecat.transports.daily.transport import DailyParams
@@ -61,10 +61,10 @@ async def run_bot(transport: BaseTransport, runner_args: RunnerArguments):
         ),
     )
 
-    tts = CartesiaTTSService(
-        api_key=os.environ["CARTESIA_API_KEY"],
-        settings=CartesiaTTSService.Settings(
-            voice="71a7ad14-091c-4e8e-a314-022ece01c121",  # British Reading Lady
+    tts = SonioxTTSService(
+        api_key=os.environ["SONIOX_API_KEY"],
+        settings=SonioxTTSService.Settings(
+            voice="Maya",
         ),
     )