The new @babel/eslint-parser fails without a Babel config in the root when you're running ESLint from the root, so I had to specify a root babel.config.js. I chose to just move the lib one to the root, as it's basically the "least common denominator" of ESLint configs in our repo

The reason we need this is explained here:

• Searching will stop once a directory containing a package.json is found, so a relative config only applies within a single package.
• The "filename" being compiled must be inside of "babelrcRoots" packages, or else searching will be skipped entirely.

These caveats mean that:

• .babelrc.json files only apply to files within their own package
• .babelrc.json files in packages that aren't Babel's 'root' are ignored unless you opt in with "babelrcRoots".

Babel does not recommend a setup with multiple babel.config.cjs files. Instead, in a monorepo you're supposed to have one babel.config.cjs file at the root, and then one .babelrc.cjs file for each package where you want to override something.

As such, I moved these per-package babel.config.cjs files to .babelrc.cjs.

Notwithstanding the previous inline comment... for reasons explained in the last paragraph of the diff description, I needed to keep the babel.config.cjs files to keep Jest working. To avoid duplicating anything, I simply reference the .babelrc.cjs files from the babel.config.cjs files.

I'm hoping eventually Jest will figure out how to use Babel's config correctly, at which point we can delete the per-workspace babel.config.cjs files. For that reason, I've updated these commands to reference the correct .babelrc.cjs files instead of the just-there-for-Jest babel.config.cjs files

This change is necessary for Jest to be able to find the root babel.config.cjs. I got from the "Jest" section of this blog post.

Curiously, I found this change necessary even after I created the babel.config.cjs alias files.