feat(cask): add cask update command to manage cask formula

This will be used by the jimeh/homebrew-emacs-builds brew tap repository
in combination with brew livecheck to automatically update cask formulas
to the latest nightly builds from the jimeh/emacs-builds repository.

pkg/cli/cli.go

@@ -49,6 +49,7 @@ func New(version, commit, date string) *CLI {
 				notarizeCmd(),
 				packageCmd(),
 				releaseCmd(),
+				caskCmd(),
 				{
 					Name:    "version",
 					Usage:   "print the version",