test: added @media at-rules test

[alexander-akait]

This PR contains a:

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

Motivation / Use-Case

more tests

Breaking Changes

No

Additional Info

Some tests are commented, due it is experimental and doesn't support any browsers yet, we should improve this and fix on css-loader side (also inside style-loader)

[codecov]

Codecov Report

Merging #818 (e230cd7) into master (f813b4c) will increase coverage by 0.27%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #818      +/-   ##
==========================================
+ Coverage   92.16%   92.44%   +0.27%     
==========================================
  Files           6        6              
  Lines         715      715              
  Branches      173      173              
==========================================
+ Hits          659      661       +2     
+ Misses         53       51       -2     
  Partials        3        3              

Impacted Files	Coverage Δ
src/index.js	96.10% <0.00%> (+0.51%)	⬆️

---

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 f813b4c...e230cd7. Read the comment docs.