Webhook for synology chat

### Feature Description

Would be nice if Gitea has support to synology chat.
Synology has a webhook support and the format is:
https://URL:15556/webapi/entry.cgi?api=SYNO.Chat.External&method=incoming&version=2&token=%22token%22

#https://kb.synology.com/en-id/DSM/help/Chat/chat_integration?version=7

### Screenshots

_No response_