Module Format

The project really never took a stance on this AFAIK. Since everything was CJS and it wasn't releasing breaking changes meant we really didn't need to take a stance. That said, due to the fact that ESM only modules explicitly drop support for the majority of the ecosystem, I would propose that the project commit to one of two options for all the packages:

1. Stick with CJS until the status changes (and pick some clear trip wire points to revisit the decision)
2. Dual publish. This would require some build tooling which we traditionally didn't need, but would keep ecosystem support.

This came up because of this issue in multer: https://github.com/expressjs/multer/issues/1245