Is your feature request related to a problem or challenge?

Currently, if we type an invalid command in datafusion-cli, it will say xx is not a valid command, such as below

> \quit
'\quit' is not a valid command

Maybe we can enhance this message to the following

> \quit
'\quit\ is not a valid command, use '\?' to see all valid commands

So that the user can know all the valid commands we support

Describe the solution you'd like

Enhance the help message for invalid commands. Append use '\?' to see all valid commands to the end of the help message.

Describe alternatives you've considered

No response

Additional context

No response