fix(cli): prevents next step until an available commit type is selected

[lincolnjpg]

Hi,

Recently, I started using git-cc and I'm really enjoying it. I've found a behavior that I don't know if is intended.

When a invalid commit type (a commit type that is not listed in the option list) is selected, user can still advances to the next screen and then to the next. But after confirming, user returns to the initial screen.

With this PR, user can only advance to the select commit scope screen when a valid commit type was selected in the previous screen.

[SKalt]

When an invalid commit type (a commit type that is not listed in the option list) is selected, the user still advances to the next screen and then to the next. But after confirming, the user returns to the initial screen.

That's definitely undesired. I'll merge this PR now and cut a release later today.

Recently, I started using git-cc and I'm really enjoying it.

I'm glad to hear that :) Thanks for submitting a PR.

[SKalt]

I'd like to alert the user about the invalid option, too, but implementing error messages (#20) isn't a blocker for this PR.

[lincolnjpg]

Thanks @SKalt and keep up the good work :)