Hacking directions in contributing.md may need attention

[krancour]

I encounter a variety of issue when following the directions on my Mac. I don't know if it's all Macs or specific to my system because of varying versions of different native tools, etc. from homebrew...

Currently, I succeed on hacking on this site by doing so from within a Node 16 container like so:

$ docker run -it -p 1234:1234 -v $(pwd):/src -w /src node:16 bash

I also run into issues if I use Node 18.

I'll update the issue with specific logs next time they pop up, but I just didn't want to lose track of this.