Fix inappropriate modification of animation keywords

[kogai]

It seems there is a case which handling animation-keywords as local-identifier incorrectly.

Originally, the issue reported at webpack-contrib/css-loader#872

[codecov-io]

Codecov Report

Merging #5 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master       #5      +/-   ##
==========================================
+ Coverage   99.56%   99.57%   +<.01%     
==========================================
  Files           2        2              
  Lines         232      234       +2     
  Branches       65       66       +1     
==========================================
+ Hits          231      233       +2     
  Misses          1        1

Impacted Files	Coverage Δ
test.js	100% <ø> (ø)	⬆️
index.js	99.51% <100%> (ø)	⬆️

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[alexander-akait]

hm, i think we need test from issue:

animation: slide-right 300ms forwards ease-out, fade-in 300ms forwards ease-out;

[kogai]

@evilebottnawi OK, I've adjusted the spec to includes some local variables like the issue 👉 bb4bec6 .

[alexander-akait]

Good work, thanks!