Offer a Homebrew formula

[AlexanderWillner]

Is your feature request related to a problem? Please describe.
Due to Apples update policy, the plugin often does not work after an OS update.

Describe the solution you would like
Offer a formula via Homebrew, analog to MailTrackerBlocker. This way it could automatically be updated, e.g. via Topgrade.

Describe alternatives you have considered
Use of a dedicated update application, similar to GPGMail, but this is much more overhead.

Additional context
The command might end up to be brew install --cask universalmailer (see https://formulae.brew.sh/cask/mailtrackerblocker for an example).