Currently using https://github.com/placemark/check-geojson for this usecase right now.

Noticed your code includes a custom JSON parser, which seems to silently overwrite duplicate keys, which is absolutely something a linter should warn about.

And instead of using fast-glob, I'd recommend https://superchupu.dev/tinyglobby or better yet, use node:fs and node:fs/promises which are built in to modern node already.

And I noticed your package.json includes some bizarre fields,

  - "types": "./dist/index.d.ts" is unnecessary since you're an ESM module and require Node >22
  - "./package.json": "./package.json" is a Node 12-14 ESM workaround