Co-authored-by: Markus Reiter <me@reitermark.us>

Anywhere we can use `blob/master` we can use `blob/HEAD` instead. This
will make life easier if we ever rename our default branch in future
(once/if Git and GitHub provides the necessary tooling to do so).

- Depending on context, I've gone for either "denylist" or "disallow"
  here. "Disallow" for things in sentences, or actions, and "denylist"
  for list of things.

In some cases, certain Casks shouldn't be resubmitted for specific reasons: difficult to maintain, developers maintain their own version, ...

To make sure these cases are restricted - we can add them to a blacklist and have the blacklist checked as part of the `brew cask audit` steps.