Distribute `bbk` CLI with Homebrew

[yermulnik]

It would be really handy for macOS and Linux users. Thanks in advance.

Refs:

• https://docs.brew.sh/Taps
• https://docs.brew.sh/How-to-Create-and-Maintain-a-Tap

[FaffeF]

Could probably be considered for a PR to homebrew-core instead of a separate tap

https://docs.brew.sh/How-To-Open-a-Homebrew-Pull-Request
https://docs.brew.sh/Acceptable-Formulae

[yermulnik]

https://docs.brew.sh/Acceptable-Formulae#niche-or-self-submitted-stuff

• be known (e.g. GitHub repositories should have >=30 forks, >=30 watchers or >=75 stars)