fix(loadConfig): added fix when loading postcss esm configs

[lideen]

This PR contains a:

• bugfix
• new feature
• code refactor
• test update
• typo fix
• metadata update

Motivation / Use-Case

I'm using a ESM version of postcss config in one of my projects (postcss.config.mjs) and noticed that postcss-loader did not pick up the configuration. This fixes that issue.

Additional Info

One of the tests I added need to be run with NODE_OPTIONS=--experimental-vm-modules to enable ESM support in jest. Flip the test to it.only and run:

NODE_OPTIONS=--experimental-vm-modules npm run test:only -t 'config-autoload'

[linux-foundation-easycla]

• ✅login: lideen / (53a2759)

The committers listed above are authorized under a signed CLA.

[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 88.30%. Comparing base (107b519) to head (53a2759).
Report is 1 commits behind head on master.

Files	Patch %	Lines
src/utils.js	50.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #684      +/-   ##
==========================================
- Coverage   88.73%   88.30%   -0.44%     
==========================================
  Files           3        3              
  Lines         355      359       +4     
  Branches      116      118       +2     
==========================================
+ Hits          315      317       +2     
- Misses         37       38       +1     
- Partials        3        4       +1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.