feat: partial compatibility with postcss-cli

[alexander-akait]

This PR contains a:

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

Motivation / Use-Case

fixes #497

Breaking Changes

No

Additional Info

Partial compatibility with postcss-cli with some limitations, please read #497 (comment)

[codecov]

Codecov Report

Merging #498 (e2c1e4a) into master (6c9f6b5) will increase coverage by 0.62%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #498      +/-   ##
==========================================
+ Coverage   97.32%   97.95%   +0.62%     
==========================================
  Files          10        5       -5     
  Lines         486      244     -242     
  Branches      158       80      -78     
==========================================
- Hits          473      239     -234     
+ Misses         12        5       -7     
+ Partials        1        0       -1     

Impacted Files	Coverage Δ
src/index.js	100.00% <100.00%> (ø)
src/utils.js	97.02% <100.00%> (+0.61%)	⬆️
D:/a/postcss-loader/postcss-loader/src/utils.js
D:/a/postcss-loader/postcss-loader/src/Warning.js
D:/a/postcss-loader/postcss-loader/src/Error.js
D:/a/postcss-loader/postcss-loader/src/index.js
D:/a/postcss-loader/postcss-loader/src/cjs.js

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 6c9f6b5...e2c1e4a. Read the comment docs.