docs(hugo): add empty chat notes

Author: iyear

docs/content/en/guide/tools/export-messages.md

@@ -9,6 +9,10 @@ Export media messages from chats, channels, groups, etc. in JSON format.
 
 {{< include "snippets/chat.md" >}}
 
+{{< hint info >}}
+Empty CHAT means 'Saved Messages'
+{{< /hint >}}
+
 ## All
 
 Export all messages containing media to `tdl-export.json`

docs/content/zh/guide/tools/export-messages.md

@@ -9,6 +9,10 @@ weight: 30
 
 {{< include "snippets/chat.md" >}}
 
+{{< hint info >}}
+空的 CHAT 表示“收藏夹”
+{{< /hint >}}
+
 ## 所有消息
 
 将包含媒体的所有消息导出到 `tdl-export.json`