Add STTMuteProcessor to un/mute the STT

src/pipecat/frames/frames.py

@@ -570,6 +570,13 @@ class TTSUpdateSettingsFrame(ServiceUpdateSettingsFrame):
     pass
 
 
+@dataclass
+class STTMuteFrame(ControlFrame):
+    """Control frame to mute/unmute the STT service."""
+
+    muted: bool
+
+
 @dataclass
 class STTUpdateSettingsFrame(ServiceUpdateSettingsFrame):
     pass