Set up our own Homebrew tap

[Ola Bini]

For now, we can't publish a Cask in the main Homebrew repository. This is partly because of #853. So in the meantime, we should consider creating our own Tap, as outlined in https://docs.brew.sh/How-to-Create-and-Maintain-a-Tap

For more information about Homebrew, see #178 and #241