feat: show an error and terminate if there are no commands defined

[eleftrik]

If no commands have been registered, it shows the user an error along with some notes to help them:

Why this check?
Because I had to struggle a little bit with this error: Undefined array key 0 {"exception":"[object] (ErrorException(code: 0): Undefined array key 0 at /.../vendor/aaronfrancis/solo/src/Prompt/Dashboard.php:77).
I encountered this error after installing solo in a Laravel 10 app recently upgraded to 11 where I manually needed to register SoloServiceProvider in config/app.php (the "old" way).

This PR could be useful to other users with a similar setup; it may also help those who have forgotten to define at least one command in the service provider (unlikely, but getting distracted is a snap 😅).

Please feel free to adjust the tone of voice of messages: they may sound too harsh 😇

Perhaps, there is also a better way (not in the constructor, I mean) to perform this little check and terminate.

Thanks for this fantastic package!

[aarondfrancis]

Great idea! I switched it up a bit to show the About comand, since that already shows some documentation. Thanks!