Add brew receipt for elastic-package

We can consider introducing another release channel for our users - a brew receipt. Compared to Github releases, this option might be more comfortable in terms of updating.

The issue provides no file, test, or release entry point to start from. First inspect how elastic-package releases are built and distributed, then identify the repository's existing release configuration and determine what Homebrew receipt format and update flow are required. Done means the tool can be installed and updated through the proposed brew channel.

Written by the indexing model from the issue text.