docs(README): add notes to message link

Author: iyear

README.md

@@ -264,9 +264,19 @@ tdl login --code
 
 > If you need higher speed, set higher threads. But do not arbitrarily set too large `threads`.
 
-- Download (protected) chat files from message urls:
+- Download (protected) chat files from message link:
+
+> **Note**
+> Get message links from "Copy Link" button in official clients.
 
 ```shell
+# message link may be like:
+# - https://t.me/telegram/193
+# - https://t.me/c/1697797156/151
+# - https://t.me/iFreeKnow/45662/55005
+# - https://t.me/c/1492447836/251015/251021
+# - file a new issue if you find other formats
+
 tdl dl -u https://t.me/tdl/1 -u https://t.me/tdl/2
 ```
 

README_zh.md

@@ -271,7 +271,17 @@ tdl login --code
 
 - 从消息链接下载（受保护的）文件：
 
+> **Note**
+> 从官方客户端的 "复制链接" 按钮获取消息链接。
+
 ```shell
+# 消息链接可能是以下格式之一：
+# - https://t.me/telegram/193
+# - https://t.me/c/1697797156/151
+# - https://t.me/iFreeKnow/45662/55005
+# - https://t.me/c/1492447836/251015/251021
+# - 如果你发现其他格式的链接，请提交 issue
+
 tdl dl -u https://t.me/tdl/1 -u https://t.me/tdl/2
 ```