Provide ESM bundle

[marvin-j97]

Most popular packages have moved on to ESM-only or dual export packages.
Moo is still using the old-fashioned UMD format, being not-really-compatible with modern tooling.

[tjvr]

Hi, can you give an example of tooling that is not compatible with Moo today?

[nathan]

I imagine "not-really-compatible" here means "it works completely fine and my packaging script can't exclude compileStates" or "it works completely fine and my editor can't autocomplete the entry point names"

[mb21]

Yeah, without ESM bundle it cannot be tree-shaken... but looking at the source, I'm not sure how much there could be shaken away anyway..?

[johndeighan]

ESM would allow this, which is a style I use all the time:

import {compile} from 'moo';