Show cask description in brew cask info command

[waldyrious]

• Have you followed the guidelines in our Contributing document?
• Have you checked to ensure there aren't other open Pull Requests for the same change?
• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your changes? Here's an example.
• Have you successfully run brew style with your changes locally?
• Have you successfully run brew tests with your changes locally?
  (partially: I ran brew tests --online --only=cask/cmd/info, and all tests therein passed.)

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Actually display Cask descriptions (introduced in #8137) in the output of brew cask info.

The approach I took here was to not display the description if it doesn't exist, instead of showing None as is done for the name(s). Happy to change it to show None if that's preferred (as descs are meant to eventually become mandatory). /cc @reitermarkus

[vitorgalvao]

If we were planning on descriptions being optional, displaying nothing would be cleaner. But because we want them to be mandatory—and filled as soon as possible—I’d go with None because that will increase user awareness of the feature, meaning we might get more contributions.

[waldyrious]

Ok, I added a commit adding the None output, and amended the previous commits to fix the failing tests that I hadn't noticed earlier.

[vitorgalvao]

Fantastic and blazing fast work! Thank you for the continued contributions.

[waldyrious]

Fantastic and blazing fast work!

I had actually implemented it this way at first, so the logic was still in RAM 😄

Thank you for the continued contributions.

My pleasure! I'm trying to get this desc stuff done while I have the time, before my vacations end at the end of this week :)

[reitermarkus]

Thanks, @waldyrious!