Adding Elastic Agent homebrew-tap

[Conky5]

Describe the enhancement: A request was made to add the Elastic Agent to the homebrew-tap repository https://github.com/elastic/homebrew-tap/issues/94

Describe a specific use case for the enhancement or feature: Using homebrew to install the Elastic Agent on macOS.

[elasticmachine]

Pinging @elastic/agent (Team:Agent)

[botelastic[bot]]

Hi! We just realized that we haven't looked into this issue in a while. We're sorry!

We're labeling this issue as Stale to make it hit our filters and make sure we get back to it as soon as possible. In the meantime, it'd be extremely helpful if you could take a look at it as well and confirm its relevance. A simple comment with a nice emoji will be enough :+1. Thank you for your contribution!