pock: Add zap stanza

[muneebmahmed]

Important: Do not tick a checkbox if you haven’t performed its action. Honesty is indispensable for a smooth review process.

After making all changes to a cask, verify:

• brew cask audit --download {{cask_file}} is error-free.
• brew cask style --fix {{cask_file}} reports no offenses.
• There are no open pull requests for the same update.
• The submission is for a stable version or documented exception.

Additionally, if adding a new cask:

• Named the cask according to the token reference.
• brew cask audit --new-cask {{cask_file}} worked successfully.
• brew cask install {{cask_file}} worked successfully.
• brew cask uninstall {{cask_file}} worked successfully.
• Checked the cask was not already refused.
• Checked the cask is submitted to the correct repo.

Adds a zap stanza for pock, thanks to https://github.com/nrlquaker/homebrew-createzap.