Refactor header length retrieval to utilize more appropriate method

src/edge_tts/communicate.py

@@ -5,6 +5,7 @@ Communicate package.
 
 import json
 import re
+import struct
 import time
 import uuid
 from contextlib import nullcontext
@@ -414,12 +415,13 @@ class Communicate:
                                 "We received a binary message, but we are not expecting one."
                             )
 
-                        yield {
-                            "type": "audio",
-                            "data": received.data[
-                                received.data.find(b"Path:audio\r\n") + 12 :
-                            ],
-                        }
+                        # See: https://github.com/microsoft/cognitive-services-speech-sdk-js/blob/d071d11d1e9f34d6f79d0ab6114c90eecb02ba1f/src/common.speech/WebsocketMessageFormatter.ts#L46
+                        header_length = struct.unpack(">H", received.data[:2])[0]
+                        if len(received.data) > header_length + 2:
+                            yield {
+                                "type": "audio",
+                                "data": received.data[header_length + 2 :],
+                            }
                         audio_was_received = True
                     elif received.type == aiohttp.WSMsgType.ERROR:
                         raise WebSocketError(