handle uallowed chat ids with an informative message

currently, the bot does not respond to messages from chat IDs that are not included in the [allowed_chat_id](https://github.com/birlug/WiseAssBot/blob/9befe269a78804c92d17573805b398a3b5c3212c/config-example.toml#L6C1-L6C17) list. would be beneficial to display an informative message in such cases.