convert to ESM only

[ungoldman]

The long winter is over.

https://socket.dev/blog/require-esm-backported-to-node-js-20

Since Node 20 is now oldest LTS (see Node Releases), and require(esm) was successfully ported to Node 20 in February of this year, it is finally fully safe to convert all CommonJS libraries that have ancient dependents to ESM (with a major version, of course).