Default output for CLI with unknown commands

[hsxfjames]

What problem does this feature solve?

If we invoke CLI with unknown commands from terminal, the CLI just ignore and exit.
For example:

vue something

It will output nothing.

What does the proposed API look like?

How about output the help information and tell users that the entered something is not a correct command or is an unknown command? It's just a small enhancement for user experience though.

[hsxfjames]

Another example is that misspelling "create" to "craete":

vue craete

will output nothing, left people confused and not sure of whether the command is succeeded or failed.