Contributing/Development guide for this repository?

[JoshuaKGoldberg]

I just sent #1281 - my first to vanilla-extract, yay! But I had to piece together a few parts of the development flow: installing, building, and changesets. They aren't documented anywhere I could find. Would it be possible to add a standard CONTRIBUTING.md file?

Steps I took to get the site running:

1. pnpm i
2. pnpm build
3. cd site
4. pnpm start

I'd be happy to send a PR, though I haven't actually built or tested anything outside site/ directory. 😄

[askoufis]

Thanks for the reminder. It's on our todo list 👍.