Add homebrew on Linux and macOS

[ClashTheBunny]

This adds directions that will work when https://github.com/Homebrew/homebrew-core/pull/105986 is merged. If that is not merged, we can create a tap and adjust these directions accordingly.

I think I followed the current formatting, but is there a specific markdown linting that is preferred? I didn't see anything in the .github directory.

Checklist

If applicable:

• [ ] I have updated CHANGELOG.md
• [X] I have updated the documentation (README.md, docs/, demos/)