fix: prefer sass/scss/css extensions

[alexander-akait]

This PR contains a:

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

Motivation / Use-Case

fixes #556

Breaking Changes

Should be no, but if you faced with problem feel free to open new issue

Additional Info

No

[codecov]

Codecov Report

Merging #711 into master will increase coverage by 0.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #711      +/-   ##
==========================================
+ Coverage   98.06%   98.07%   +0.01%     
==========================================
  Files           6        6              
  Lines         155      156       +1     
==========================================
+ Hits          152      153       +1     
  Misses          3        3

Impacted Files	Coverage Δ
lib/loader.js	100% <100%> (ø)	⬆️

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[alexander-akait]

may i ask what the '...' additions mean (here and the line below)?

it extends you default configuration, you can use global mainFields https://webpack.js.org/configuration/resolve/#resolvemainfields, to avoid break logic we just extends them

does this change mean i can use the "style" field in package.json?

yes, you can use sass and/or style field in package.json