Add example on how to send a message to a channel

Perhaps in `on_message` using the `c` handle, it might be easy.
But if you access the server object from outside a event-driven event, it seams extremely complicated to *figure out* how to send messages.

Overall, documentation other than auto-doc strings would be pretty helpful.

Start by locating the project’s documentation and the message-sending entry points referenced in the issue, especially on_message, the c handle, and access through a server object. Add a clear example for sending a channel message outside an event-driven handler, and ensure the broader documentation request is addressed or scoped explicitly.

Written by the indexing model from the issue text.