macOS binaries

[gnprice]

Much like #3 for Linux, it would be good to publish binaries for macOS.

(At least one person has specifically asked about installing on macOS: @serpa-dystematic, at #9 (comment) .)

[timsutton]

I've done this via cargo install toml-cli but it could be sweet if this was in homebrew/core!

[chicks-net]

I could help with this, but given #29 I'm not going to worry too much about it.