Add monorepo tooling

[jgaehring]

Since #446 we've effectively had a monorepo, and that's only grown since then, especially with #491, but that last one introduced issues I don't think are thoroughly resolved yet. Namely, it's not great to be importing field-scripts and field-kit itself with relative paths in the dependents' package.json, and obviously that won't work in community modules, so I think it's time to bring in Lerna or something made for this kind of set up.

Found some helpful resources:

• https://www.letsdebug.it/post/12-monorepo-with-vue-vite-lerna/
• https://github.com/vitejs/vite/issues/1491
• https://github.com/adiun/vite-monorepo
• https://github.com/LinusBorg/vue-lib-monorepo-template

[jgaehring]

Ultimately, I decided to just use npm's built-in workspaces, at least for now, since it doesn't require any additional devDependencies. Tools like Lerna or Yarn might still prove useful for automation in the future.

Resolved by the following commits:

• 494ed81 Rename field-kit/core to field-kit/src.
• b59327b Make components their own farm-ui package.
• 103630b Add Netlify config file; remove _redirects file.
• b1ac71f Fix path to field-kit in develop-module script.
• e754d59 Move src to packages and init npm workspaces.