Support loading ECMAScript modules, but drop sync API (#230)

michael42 commented 2 years ago

`Notable Changes`

This PR implements support for .mjs config files (and .js config files within "type": "modules" projects). To support that without much hassle, support for synchronously loading configs is dropped, as ECMAScript Modules are loaded inherently async.

`Commit Message Summary (CHANGELOG)`

commit message body...

`Type`

[ ] CI
[X] Fix
[ ] Perf
[ ] Docs
[ ] Test
[ ] Chore
[ ] Style
[ ] Build
[X] Feature
[X] Refactor

`SemVer`

[ ] Fix (:label: Patch)
[ ] Feature (:label: Minor)
[x] Breaking Change (:label: Major)

`Issues`

Fixes #230

`Checklist`

[X] Lint and unit tests pass with my changes
[x] I have added tests that prove my fix is effective/works
[x] I have added necessary documentation (if appropriate)
[ ] Any dependent changes are merged and published in downstream modules

ai commented 2 years ago

I will put this task on a little hold until Node.js 12 EOL

binyamin commented 2 years ago

I will put this task on a little hold until Node.js 12 EOL

@ai That time has come. See the release chart.