Fix Python 3.7 compatibility issue (#404)

Fixes https://github.com/rany2/edge-tts/issues/403

Signed-off-by: rany <rany2@riseup.net>

src/edge_tts/communicate.py

@@ -16,7 +16,6 @@ from typing import (
     Dict,
     Generator,
     List,
-    Literal,
     Optional,
     Tuple,
     Union,
@@ -25,6 +24,7 @@ from xml.sax.saxutils import escape, unescape
 
 import aiohttp
 import certifi
+from typing_extensions import Literal
 
 from .constants import DEFAULT_VOICE, SEC_MS_GEC_VERSION, WSS_HEADERS, WSS_URL
 from .data_classes import TTSConfig

src/edge_tts/data_classes.py

@@ -5,7 +5,8 @@
 import argparse
 import re
 from dataclasses import dataclass
-from typing import Literal
+
+from typing_extensions import Literal
 
 
 @dataclass