esm version imports non esm scripts from date-fns

[trading-peter]

Hi @marnusw,

thanks for your awesome project.

I'm working on a project that only uses es modules and therefore doesn't have a transformation step for other module formats. When I imported date-fns-tz I got an error that some modules don't export a default.

So I investigated and found out that the esm functions don't import from date-fns/esm but from date-fns directly (example: https://github.com/marnusw/date-fns-tz/blob/master/src/zonedTimeToUtc/index.js#L1).

I edited your build script to modify the paths. I hope I got that hole situation right?