processors(realtime-ai): add support making TTS to speak

src/pipecat/frames/frames.py

@@ -177,6 +177,15 @@ class LLMMessagesUpdateFrame(DataFrame):
     messages: List[dict]
 
 
+@dataclass
+class TTSSpeakFrame(DataFrame):
+    """A frame that contains a text that should be spoken by the TTS in the
+    pipeline (if any).
+
+    """
+    text: str
+
+
 @dataclass
 class TransportMessageFrame(DataFrame):
     message: Any