add docs for timestamp on ForceEndOfUtterance

docs/speech-to-text/realtime/turn-detection.mdx

@@ -111,6 +111,15 @@ The `ForceEndOfUtterance` message is sent to the server to trigger an end of utt
 }
 ```
 
+For higher accuracy you can add an (optional) timestamp parameter to the message. It is the timestamp of the audio data that corresponds to the force end of utterance request. 
+It's the number of seconds since the beginning of the audio. 
+
+```json
+{
+  "message": "ForceEndOfUtterance",
+  "timestamp": 63.5
+}
+
 You can also use `ForceEndOfUtterance` with multi-channel diarization:
 
 ```json

spec/realtime.yaml

@@ -393,6 +393,11 @@ components:
         channel:
           type: string
           description: The channel to request finalized transcript from. This field is only seen in multichannel.
+        timestamp: 
+            type: 'number'
+            format: 'float'
+            minimum: 0,
+            description: "Timestamp of the audio data that corresponds to the force end of utterance request. It's the number of seconds since the beginning of the audio."
       required:
         - message
     SetRecognitionConfig: