Add support for syntax name mapping.

[gucong3000]

Closes: stylelint/stylelint#3325

[codecov]

Codecov Report

Merging #19 into master will not change coverage.
The diff coverage is 100%.

@@          Coverage Diff          @@
##           master    #19   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files          11     11           
  Lines         241    244    +3     
=====================================
+ Hits          241    244    +3

Impacted Files	Coverage Δ
index.js	100% <ø> (ø)	⬆️
parse-style.js	100% <100%> (ø)	⬆️
syntax.js	100% <100%> (ø)	⬆️
get-syntax.js	100% <100%> (ø)	⬆️

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