Refactor into a pnpm workspace

[jakebailey]

Fixes #81

Outstanding questions:

• Should it really do build-all on prepare?
• Should site be a part of the monorepo?
  • If so, should build-all build the site?
• Should I add a corepack version specifier for pnpm, or will people be able to figure out how to install pnpm themselves?
• Would you benefit from something that helps bump the version numbers in the examples? I'm not sure what this would be other than something like changesets.

Theoretically I can attempt to do this via plain npm though @DanielRosenwasser had problems with it hence asking me to send this PR for real.

[DanielRosenwasser]

Should it really do build-all on prepare?

I'd prefer it didn't, but our docs would need to be updated if that changes.

Should site be a part of the monorepo?

No, I want that to stay out of everyone's way.

Should I add a corepack version specifier for pnpm, or will people be able to figure out how to install pnpm themselves?

I don't think it makes much of a difference, right? If we did this, would it work out of the box for anyone with Node 18+? Or would people have to run a command?

Would you benefit from something that helps bump the version numbers in the examples? I'm not sure what this would be other than something like changesets.

I can just run that manually I think. It doesn't need to be a script.

[jakebailey]

No, I want that to stay out of everyone's way.

Do you want me to convert that to pnpm just so it's not mixed package managers?

I don't think it makes much of a difference, right? If we did this, would it work out of the box for anyone with Node 18+? Or would people have to run a command?

People still have to run corepack enable, it's just that you will only be using one version of pnpm, which I'd argue is better (this is how I have it set up on TS).

Would you benefit from something that helps bump the version numbers in the examples? I'm not sure what this would be other than something like changesets.

I can just run that manually I think. It doesn't need to be a script.

Right now there's no script or anything; you can technically leave the old specifiers in but pnpm won't help you update them everywhere as far as I know.