docs: Add documentation for various features including Aria2, direct download links, parsers, storage rules, silent mode, storage transfer, chat watching, and yt-dlp video download

- Created new markdown files for Aria2 download, direct download links, parsers, storage rules, silent mode, storage transfer, chat watching, and yt-dlp video download.
- Included usage examples, configuration instructions, and detailed explanations for each feature.
- Translated documentation into Chinese for accessibility.

docs/content/en/usage/watch.md

@@ -0,0 +1,36 @@
+---
+title: "Watch Chats"
+weight: 4
+---
+
+# Watch Chats
+
+{{< hint warning >}}
+This feature requires enabling UserBot integration.
+{{< /hint >}}
+
+You can watch messages in a specific chat and automatically save them to the default storage, following storage rules. You can also add filters so that only matching messages are saved.
+
+Watch a chat:
+
+```
+/watch <chat_id/username> [filter]
+```
+
+Stop watching:
+
+```
+/unwatch <chat_id/username>
+```
+
+Filter types:
+
+## msgre
+
+Regex-match the message text. For example:
+
+```
+/watch 12345678 msgre:.*hello.*
+```
+
+This will watch the chat with ID `12345678`, and only save messages whose text contains `hello`.