Respond to command calls with invalid / missing arguments

[joseywoermann]

Is this a Command (activated) or Plugin (passive)?
No.

Describe the feature you'd like
If a user runs a command that requires arguments to be passed (like .weather <location>), but does not pass the required argument(s), the bot doesn't respond or give "feedback" that it's missing arguments.

This might make some people think that the command isn't activated or that something went wrong, even if that's not (really) the case.

I think that it would make things easier / less confusing, if the bot would respond with a simple "you are missing some required arguments, check .help <command>"-message.

[joseywoermann]

Ok, with Slash Commands (#821), missing arguments won't be an issue anymore (The UI enforces them).
But I would leave it open anyways, because nice error messages are always useful. (These could also be ephemeral)