docs(README): add chat export

Author: iyear

README.md

@@ -213,6 +213,21 @@ List all your chats:
 tdl chat ls
 ```
 
+Export minimal JSON for tdl download (NOT for backup):
+
+```shell
+# will export all media files in the chat.
+# chat input examples: `@iyear`, `iyear`, `123456789`(chat id), `https://t.me/iyear`, `+1 123456789`
+
+tdl chat export -c CHAT_INPUT
+
+# specify the time period with timestamp format, default is start from 1970-01-01, end to now
+tdl chat export -c CHAT_INPUT --from 1665700000 --to 1665761624
+
+# specify the output file path, default is `tdl-export.json`
+tdl chat export -c CHAT_INPUT -o /path/to/output.json
+```
+
 ## Env
 
 Avoid typing the same flag values repeatedly every time by setting environment variables.

docs/desktop_export.md

@@ -1,6 +1,15 @@
 ## Get desktop clients exported JSON
 
-1. Choose the dialog you want to export, and click the three dots in the upper right corner, then click `Export Chat History`.
+There are two ways to export the JSON you need
+
+### TDL (especially for protected chats)
+
+Please refer to [README](../README.md#chat-utilities)
+
+### Official desktop clients
+
+1. Choose the dialog you want to export, and click the three dots in the upper right corner, then
+   click `Export Chat History`.
 
 2. Uncheck all boxes(you don't need to download them now) and set `Size Limit` to minimum